I wrote an article on caring for a chick with a severe wound. It's the first link listed below this post and may have some info you'll find relative to your situation.
The important thing is to keep the wound clean and moist. Once the wound is cleaned of all foreign material, spraying with Vetericyn, a coating of Blue-kote, and once that dries, a smearing of antibiotic ointment will promote fast healing, but only if you do it every day until the wound completely heals.
The chick will be better off back with its mates, and the Blue-kote will help prevent them from molesting the wound. Granted, chicken environment is a dirty one, but with twice-a-day cleansing, and the wound dressing I recommended, the chick will heal without infection.