Children develop habits which can be worrying. Sometimes they go away in time.. I agree with Sustainable Sue's suggestions also. I'd like to know the following:
1. How old is he?
2. When did you noticed he first started biting his fingers?
3. Were there any changes in his routine?
4. Were there any problems you or your family members may have been going through at that time and since?
5. If he is school age, do you know if he has had negative experiences there?
6. Has someone important to him left?
7. Does he have a sibling?
8. Any changes in his sleep pattern?
9. Is he alone a lot?
10. Was the a thumb/knuckle sucker as an infant?
There are many factors to consider. Why not contact me by email so we can look into this further for you.
I hope this helps
Helen Lewis DHP MNRHP