Yes, tell your parents, please.

Are you worried that you hit your head, without knowing, during an absence seizure or a fainting spell? Or just hit it and can't remember because of the injury?

Try and rest, if your symptoms get worse, get it checked out at the ER.

When I'm anywhere I think my head could get whacked (like watching a ball game), I wear a Forcefield concussion band. They look pretty much like a sweatband, but offer some protection from external blows.
www.forcefieldheadbands.com