PLEASE READ HELP!:I accidentally threw a empty water bottle at my brothers forehead and the cap hit his head.?

It left a small lining mark on his head (this happened about 14 hours ago, and I threw it to intentionally hit the bed 3 feet away from him, (I am 13 and he is 14) and he cried for a bit then stopped, I had him put a bag of ice on his head, where it was and he said he had a head ache. I staid up for hours googleing as much info as I could find. I am scared and I dont know if he might have a mild concussion, because sines of this stuff dont always appear immediatly (I havent told our parents) I tested to see if his eyes dialated correctly when light hit them, and they dialated correctly, his pupils are the same size,so thats good, but I had him sleep it off, and he still had a slight mild head ache when he woke up, and we just ate taco bell, and he ate sum sort of mexican ice ream (i told him not to) and now he feels like he wants to sleep, nautious which can be caused by a mild cuncusion or the bad food. I am freaked out and nees serious answers, and help right away. (by the way the bottle hit him from 4 and a half feet away). Help, and thanks to the people who care.