"I got stabbed in the abdomen but LUCKILY it didn't hit anything important!" drives me completely fucking insane as someone who knows anatomy, just saying. You've got your intestines in there; try stabbing a sausage and sewing the skin back on, go on. Sausage skins are literally intestines. Look how thin they are. That shit is DELICATE!
Along those lines if you get stabbed in "the side"... your large intestines are there. That's where all the poop is. You get poop in your open wound you are dying in agony without surgery because it's poop and it's riddled with bacteria. Because yeah your bowels will have to be stitched up.
Abdomen wounds are agonising because if your bowels don't open up and drown your wounds in poop, it's your intestines or stomach drowning your wounds in acid. Also you need your abs to sit up. You need your side to twist the around. Nothing in your body is redundant.
A lot more wounds need surgery than you think. A lot of broken bones need surgery. Pre-modern medicine this meant disability. Pre-modern medicine a compound fracture was a death sentence.
Sometimes pain takes a few days to REALLY kick in. My dad broke seventeen bones in a car accident and kept declining pain relief because he was totally fine. He eventually gave in because different doctors kept suggesting it. Four days later, even with that pain relief, he could barely talk, he was in so much pain.
Which reminds me, what's with the sheer amount of fantasy stories with no pain relief??? Everyone focuses on healing the wound but nobody acknowledges pain exists except for the, like, first five minutes, and then after they get medical attention it's just a bit sore at most. A lot of stuff people treat like bruises will actually drop your character for weeks.
Your character doesn't just have to worry about broken bones if they get tossed against a wall, their organs might get hurt as well. And if they have benign cysts on their organs, those could burst. I've seen a lot of kidney cysts in ultrasounds, if you wind up in a bad enough car accident those are bursting. Have fun!
Stuff often hurts either more or less than you'd think. I met a guy a few weeks ago who didn't know he broke his fucking NECK for thirty years because it was just sore now and again. Meanwhile my dad - most of his breaks were ribs, which authors tend to treat as a mild inconvenience. He had spine breaks too (and a burst kidney cyst, see above) but he said the ribs were worse. That's because just breathing moves them and you can't just stop breathing... and even if you could, your ribs will heal wrong because they'd heal too rigidly.
Someone further up talks about how pain is an alarm system and adrenaline is only part of the reason why pain signals are suppressed. Well, that is, in fact, how adrenaline works. Your unconscious mind isn't going "wait until the bear goes away THEN we'll hit her with pain signals!" because your brain is not that smart. What's actually happening is that the adrenaline is suppressing the alarm system. That's literally how it works. It's not separate, it's part of it. Different neurotransmitters and hormones can enhance or suppress pain. Adrenaline is one of the more powerful ones.
Minor injuries can be more deadly or disabling than you think. You can fall over, hit your head and die. Major injuries can also be more survivable than you think. People have shot themselves in the head with a shotgun, blown off their jaw and face, and lived. There's a lot of myths about which parts of the body are the most and least valuable. As pointed out above, a shoulder wound is a lot more deadly than you think.
"My character got a horrible injury but LUCKILY it didn't hit anything important so they are back up and running around like nothing happened after a short rest!" just give your character a stubbed toe. a stubbed toe is what you want. just give them a stubbed toe. George R R Martin was such a breath of fresh air because he never chickened out of disabling his characters, killing them, or giving them extended recoveries, and he didn't treat prosthetics as 1:1 replacements for the limbs they're standing in for. the tendency of authors to chicken out of hurting their characters has completely destroyed the drama of characters getting hurt for me because every time I read a story and a character gets hurt I KNOW the truth is author is going to cop out because they ALWAYS cop out and just pay lip service to pain like they just had a fucking stubbed toe. just give them a stubbed toe istg.
(I know as prev said that sometimes you just want to write a particular story and they're absolutely right, but this will never not drive me insane. if you're writing hurt/comfort fanfic then yeah I'm expecting a full recovery like nothing bad happened because that's the convention, but authors who play up the drama and pretend they're going to take it seriously only to wind up yanking my chain AGAIN is a particular pet peeve of mine)