You're welcome~ 

I think they sell rings or something like that with movable parts to help with fidgeting/boredom that you can try to help keep your hands away from your mouth. Maybe your goal is to stop biting your nails because it hurts or because it is doing more harm to you than good. It doesn't have to be a large goal, just one that you know isn't going to impossible or crazy (like growing your nails out so you can file them into claws in order to gouge out eyes or something...)