I'm no doctor 'K? But this happened to my son at 2 also. Same kind of presentation(he took a spill in the yard and hit his head), their skull sutures are closed by 18 to 20 months but getting knocked around is still very traumatic for them and their tender brains. I THINK this sounds normal pal but I do not envy you the night you're going to have.
Oh were the doctors pediatric specialists? If so try to trust them but keep a watch over him. Trust your instincts as well and bug the **** outa the doctors if you're worried.
all blessings pal