If you can't pass the background check you are hosed, end of story.
You'll be forced to sell to the FFL who is holding it more than likely and probably at a loss. You might convince him to hold it while you find a buyer, maybe not though.
Any pawn shop that sells or buys firearms must have an FFL. They are required to run their OWN background check on any customer wanting to buy a gun.
Also I don't know of any gun dealers who'll run on down to a pawn shop to help you buy a gun somewhere else