If I have suffered a concussion, does that mean I have suffered a permanent brain injury?

No.  Fortunately, people who suffer a concussion do not necessarily suffer a permanent brain injury.  In fact. most do not.  Nevertheless, full recovery from a concussion can take many weeks, many months, or even years.  There is a growing body of medical research that has discovered that repeated concussions can lead to severe brain damage, particularly in athletes.