My Son Age 20 Was Playing Ultimate Frisbee Just Now,

My son age 20 was playing ultimate frisbee just now, and hit the back of his head on the tennis court when he fell trying to catch the frisbee. A nurse phoned and said she was quite sure he had not been knocked unconscious at all, and most likely no concussion. My son said the back of his head hurt somewhat. I am wanting him to check in with the college campus MD at the health center first thing in the morning. If being very prudent when should he return to play ultimate frisbee? There is a tournament beginning March 15-19 I believe. Also which would be better an MRI or a CT scan or are they both irrelevant? Could he wait on the scan until he returns to Maine in 2 weeks? Thank you.