[Normally, he'd be complaining how he doesn't really know any of it, either, as figuring out magic stuff doesn't have a good track record for him -- but instead, he places a hand on Porthos' arm.]
Hey, we'll figure it out, okay? And whatever it is, it's not like it's gonna last forever, either. Hey, it might even not be anything big! If you haven't noticed it yet, I mean, it's probably nothing life-threatening. I hope.