If you got a concussion through your helmet, you should send it back and get it checked out under shock protection. Its a win win, if they don't give you a new one, you have a safe helmet, and if it is deemed unsafe, you get a new helmet. Unless of course you had large amounts of priceless stickers on it, there shouldn't be a big problem. Send it in to be safe.
'Thanks for ripping off my friend. He has a magnum.' - SkogenJake