This happened way back, but just got my attention for no apparent reason.
When I was around 7-8, my brother and I accidentally headbumped each other when trying to pick something up the same time.
The hit was on the top of my forehead (which is AFAIK like to strongest part of the skull).
The collision did not hurt at all, not the place of contact, no headache whatsoever. There was no bump on my scalp afterwards.
No loss of conciousness, no dizzyness, no difficulties in execution etc etc so basically no symptoms -
except that for like a second my vision darkened, in the same fashion when you suddenly stand up.
Why do you think this happened? Do you think there was some injury to the brain afterall?
Thanks for the answers :)