[Luckily he finds no insult in it; what's practical for a musician is not practical for a... er... pseudo-Witcher? He really needs a better title for her. Perhaps Battle Daughter. Ooh, that sort of has a ring to it. Daughter of Battle? Less familial ties that he has no claim to.]

Oh. [He clears his throat suddenly.] I didn't realize you saw that.

[Not that he was particularly ashamed of it or anything, but it had been a petty enjoyment in the moment. And considering Ciri has some sort of... of respect for her...

Well.]

It's certainly not my most skilled spell, but we can start with that. [To be fair, he only knows, like... three. Still.] Er, do you have a knife by any chance? We can start on something small.

[It totally makes sense to him to practice on a real injury.]