Biting your nails can be damaging to your teeth because your teeth are not meant to bite on or chew through your fingernails.
But other than that the biting of your fingernails will not cause any permanent damage to your fingernails.
Your fingernails will eventually grow back even after you bite the fingernails.
I used to bite my fingernails often as a kid and teen but eventually stopped doing it because it was causing teeth problems.
So I would try to avoid biting your fingernails or chewing on your fingernails if possible.
Your teeth is what will suffer from damage when you bite your nails.