Hi, My Little Cousin Is 3 And She Fell Off

hi, my little cousin is 3 and she fell off a chair and hit the back of her head on the floor. she was crying for maybe a little more than 5 minutes and went to sleep for a bit. maybe about an hour later she woke up and seems to be fine and back to normal, but I'm just wondering if there's anything I need to be concerned of ? or that I should watch after ?