Well as a child my dance teacher told me that all the bacteria that grew under my nails would form worms in my stomach, and as a five year old I believed her. Then I went back to it when I was in middle school, bullying and the such, then my grandmother told me the chemicals in my nail polish would eat a hole in my stomach, I was very freaked out by stomachs at a young age. For a while I just fascinated myself with nail polish and forgot about biting them. There's my story.

They make nail polish that is supposed to keep you from biting, Bitrex I think it's called. If not use the hair tie method. Every  time you think about biting snap a hair tie or rubber band on your wrist. I hear it works.

Best of luck!