Maybe you should put something on your fingers, toes and nails that is not unhealthy for him but that he does not like? I'm not sure what
that would be, but if you can think of something it might be worth trying.. It can often be helpful when creatures go chewing on walls and cages and all that, so it would only be logical if it helped this problem to, as long as there is'nt something you do that makes him feel threathened, and out from what you write I do not think so.
Your english seemed pretty fine to me, at least here!