I do not personally have this problem, but I worry about my 13yr old. He excessively chews on the skin around his fingernails. To the point that they are all in different stages of healing. I will catch him doing it at different times. So I don't think it is just nervous, I think it has become a habit. I am afraid he is going to ruin his nail bed and destroy his nails. (yes it is that serious) I am surprised it hasn't gotten infected yet. Next time he has a doctor visit I am going to talk with the doc about it.
Sorry I don't have any advice but you are not alone.