My symptoms got worse for about a week or 2 after I had a concussion. Then they started going away gradually. It may take even longer than 3 months for him to get better depending on the severity of the concussion. Research shows that the majority of people make a complete recovery in 3 - 6 months. I would make sure he gets plenty of rest and stays away from stressful activities and I would definitely not let him wrestle or play contact sports any time soon. There is not a whole lot you can do, except just wait for it to heal. If he hasnt had a CT scan or an MRI, I would get one and see a neurologist, just to make sure that there is no visible damage to the brain. I have been through 2 concussions and I can tell you its not fun, but the vast majority of people heal completely. It just takes time. This page has some good links on it for PCS info ->
http://en.wikipedia.org/wiki/Post_concussion_syndrome