Geralt arguing with Jaskier, trying to convince him not to do something incredibly stupid.
Jaskier, naturally, refuses to listen.
So Geralt decides to shut him up the only way he can think of: by kissing him.
There has been enough sexual tension between them for a while that Geralt wanted to do it anyway. This just happens to be a convenient excuse. It stops Jaskier from doing something reckless and gives Geralt exactly what he’s been trying very hard not to want.
What Geralt should have remembered, though, is that the only thing this petty bard loves more than Geralt is winning an argument.
So Jaskier simply puts a hand over Geralt’s mouth, pushes him away, and says:
“I am absolutely going to react to that later. But we are not done here.”