People in the ADHD community have found pick pads useful for stopping fidgeting from turning into nail biting or skin picking. You do the picking to an object instead of yourself.
 
Estimated Transit Time: 7–14 days

Three (3) pick pads with raised beads you can peel, pick and press back down. They give your fingers something to do instead of going for skin, scabs or nails. They're small enough to keep in a pocket, on your desk or by the couch.