might be able to heat it up a bit push it out and get something to hold till cooled down ?? worth a punt..
Yeah, heat is good, not too much though, I nearly killed an arch once with a heat gun.. Borrow a hairdryer, with the bumper removed gradually heat up the dented and surrounding area (which is important as the stress of the dent is at the edge of it). Then as said, you need to put preassure on it from behind and keep it there until it cools. See if you can wedge something between the plastic and the metal...
