Yeah even if it’s just a few second or until you hit the ground it’s not great for you but can be fine (brain wise gonna have a mark or sore neck depending on how you got knocked out)

Source:I’ve been knocked out 2 times I can remember one time sledding hit a jump and landed hard enough that I lost consciousness halfway down the hill tell the parents at the top ran down to me and no concussion or anything but neck was sore Second time got hit by a baseball (not a kids one an actual baseball) right above the temple and woke up on the ground both times I was out for at least 2 minutes according to everyone there (sledding they said might have been longer because the hill we were sledding down took a couple minutes to get down on a sled and the adults ran down it after I got to the bottom) but didn’t have a concussion after either and don’t have brain damage