You don't have to pass out to have a concussion. Some people will have obvious symptoms of a concussion, such as passing out or forgetting what happened right before the injury. But other people won't. With rest, most people fully recover from a concussion. Some people recover within a few hours. Other people take a few weeks to recover.
It's important to know that after a concussion the brain is more sensitive to damage. So while you are recovering, be sure to avoid activities that might injure you again.