I have the same problem, except I'll sometimes end up chewing them so much that one finger will bleed in-between the finger and nail on the side. In fact, I'm pretty sure I have dried blood under one of my fingernails.
I used be a an absolute fiend for biting my nails. What fixed it was buying a little Swiss army knife nail set. It's got a wee little nail clippers and file. It fulfilled the need for nervous movement.
Oh I can relate with this. I've recently managed to stop (hopefully for good) for the silliest of reasons. I want nice long nails.
I know it sounds silly, but I've switched from biting my nails to running my finger tip along one of my nails instead. I admire how nice they feel and it somehow takes the biting impulse away.
One thing I do need to do is an almost daily filing to keep them completely smooth. I know that I'll resume biting if I find an irregularity or a jagged edge.