I became very aware of the dangers of head injuries when DS had a serious concussion as a result of sports. He was tackled and became disoriented immediately afterwards, failing to respond to a verbal instruction by the coach, just walking around in a circle. He was taken off the field immediately, attended to with ice on his head and completely restrained by the trainer, asked to repeat certain sequences (months of the year, which he got wrong) and combinations of random numbers in small groups.
He was referred immediately to a sports injury doctor, who prescribed complete rest for a week, after putting him through a series of simple memory trials, lengthy eye exam and the sort of eye testing that a doctor does with a baby -- having him follow her finger with his eyes, etc.
What complete rest meant was no visual stimulation, no physical exertion at all, for a week. So he had to sit on the couch, no reading, no watching tv, no computer, no phone or texting. He thought he would go nuts from boredom, so we asked if he could listen to the radio a bit; the dr said only for a bit and nothing serious or no ongoing plots, so inane radio it was for a while each day. He could walk very slowly upstairs to bed, assisted. He could walk downstairs very slowly in the morning, assisted. He was to stay in bed when he awoke in the morning (no alarm clock, just me quietly calling him) and leave the bathroom door open when he was in there.
When a week was over, he had improved greatly, but he couldn't go back to sports for a while. School was just starting, and the doctor was concerned about him carrying his books around the school, up and down stairs to class, etc., so he got a note excusing him from having his full compliment of materials, and also excusing lateness to class if he couldn't get to some rooms on time.
Here's an article on children's head injuries. They can be very serious and require aftercare if complete recovery is to take place. I would suggest taking your DC to have him evaluated by a sports injury specialist or orthopedist or neurologist.
I'm shocked that the absence of a temperature combined with the report of the fall didn't immediately suggest concussion. The signs were classic.