Car door lock cover plate is stuck open

I'm a locksmith so I see this all the time. Its probably not stuck. More likely the spring or the cover itself has slipped out of position which means it would need to be taken apart to be fixed. If you use it often enough with the key then you really do not need to do anything and it will be fine. If you use a remote usually and rarely the lock then you may want to lubricate it once in awhile and cycle it with your key to keep the wafers from getting stuck by built up of dirt/corrosion.