J.,
Yes - I deal with this same "issue" with my 2 children. My daughter started doing this when she was 2 or 3 years old. She doesn't bite her nails, but she will pick her nails and when they are too short, she picks her skin.
Her younger brother had never copied the habit, but in the last 6 months or so, I've noticed him doing the same thing.
I have always attributed it to being a bad habit, like nail biting. As far as I know, we are a fairly normal household and try to stay in a routine, so there should not have been any factors in my children's lives that would have "caused" this behavior.
We are VERY firm with them when we catch them doing this, because they HAVE made their fingers bleed before. So far, we haven't been able to break the habit, but have slowed it down. Warning: in the summer, when we've been at the pool or the beach, they will also pick their toes. Watch your son for this behavior too.
If your pedi tells you this habit has a name, I'd love to know. Good luck!!!
C. B
Dahlonega, GA