It is important to take him to the dentist for xrays and an exam. Our daughter knocked her tooth loose, but not out. It discolored but we monitored it to make sure it wasn't infecting the permanant tooth above it with all the trauma. aparently as the new teeth absorb the roots of the old tooth there can be issues with damaged roots. we almost had to yank the dead tooth out, but it is absorbing fine and not affecting her new permanant tooth. If his permanant tooth is affected then you will have problems down the road. baby teeth are just for the first few years anyways.
If it was knocked out, you'll just have to wait for his 'big boy' teeth to come in. get his teeth checked out and monitor it. good luck.
good luck