msula.. I sympathise.. when i was a teenager i was cutting something with a razor blade and damn nearly took the top of the first finger off - it was close they saved it and eventually i got some feeling back, I also did something to the 2nd finger in which lost it's feeling at the top (can't remember was probably drunk at the time) it didn't help much learning to play the guitar. BTW I think Tony Iommi cut the tops off (the same two fingers) i don't know how he recovered.

The up side is that i recovered an amount of feeling in those fingers and i hope your thumb recovers as well as my fingers did..can take a long while,but if you get it checked from time to time maybe the doctors can help you out. Hope you recover well.