What Should I Do For The Vomiting Followed By A Fall?

my 9 yr old son fell face forward 36 hrs ago at his basketball game. He did NOT lose consciousness, he did NOT have bruising. In fact he immediately got up and finished the game. He has been active since it happened. He has had NO headache, NO dizziness and NO symptoms, but about an hour ago he began vomiting and did so three times. He has no complaints other than an upset stomach. He ate fine. Acted completely and absolutely normal with only the vomiting occuring tonight. He does NOT have a fever though. A bad flu has been going around his school lately. Do you think it could be a concussion. I don't think it is based on his symptoms but better safe then sorry. Ought I take him to the hospital immediately? Should I do anything at all beyond watching his behavior for the next day or so? If you do think I should take him in is it okay to do so in four hrs as it's the middle of the night here by us? Thank you so much