What Causes Swelling And Pain In The Throat Post Injury?

My 17 year old son was playing football with friends a week ago and accidentally took an elbow to the throat. That day it hurt of course and he had trouble get in his breath back and soon after seemed fine. He only complained of a sore throat. It has been a 9 days and his throat looks swollen and still hurts. Is this any cause for alarm, or is the swelling normal?