Haha I do this as well. I used to be a really bad nail biter up until a few months ago. However i still bite the skin around my nales. they eventually start hurting and all that but I just can't stop.

The other day I was actually getting a manicure and the lady making my nails look soo manicured actually told me that there are alot of people that do this. I felt sorta better. I just need to stop biting the skin around my nails and maybe start biting my hand or somehting and eventually nothing at all lol.