"I hope you're not getting bored," he says, absently and slightly too fast, as he goes back to the Sympathy/Conquest approach and considers the problem with his spare attention.
He asked what this universe knew about and healing magic wasn't, actually, specifically on the list. So maybe you have to - construct an understanding out of local pieces. He doesn't have any local pieces, and also that's annoying. But okay, what are some alternative avenues? Experimentation is safe here! He can just try things and see where trying gets him!
People heal naturally on their own without magical intervention; can he request that her finger do that on a highly accelerated schedule?