Is the wound deep, or is it a skin tear? My question is really are any of it insides visible?
If it is a simply laceration to the dermis (outer, middle or even inner - i.e., fat layer) you can just wash it with either a clorhexidine solution or iodine solution. Pat dry the area. Cut the surrounding feathers (make sure they are not pin feathers - i.e., growing in feathers), Cutting the surrounding feathers aways helps the skin to gradiate back in without interference. You don't want the feathers growing into the healing skin. Then apply a triple antibiotic ointment without pain killer in it. Do this 2-3 times a day. After the scab starts to form you can stop with the daily washings and just keep the wound moist - a moist wound heals more comfortably than a dry wound.
If the chick continues to peck at the wound you may have to wrap her loosely so she doesn't keep opening the wound.
If the injury is beyond the dermis, then a vet vist may be in order as it may require oral antibiotics to heal.
If you are going to keep he chick, this will be a good isolation period. The wound will take at least a couple of weeks to heal, but maybe longer.