As long as the chick is not having severe breathing problems or it is not getting huge, it should be left alone to be absorbed by the body. Let us know how it gets along.
Is there any feeling of air under the skin or does it feel more solid or like fluid? It sounds almost like an injury from flying or running into something. A leaking air sac (subcutaneous emphysema) can occur with blunt trauma. Is she eating and drinking? Can she walk and get around?