I had to replace the rear bumper due to a wreck. It's an oem bumper (new). It fits fine all through out except for where it sits up against the fender underneath the gas lid. The bumper sticks out just a bit, as if it's not clipping on the black thing. I can push it in but it'll work it's way back out.

Is there an easy fix to this?
What would it take to fix it?

I'll try to post pics later when I can

 

You said your car was in a wreck? My guess is that maybe something worked it's say out of shape? Wouldn't be able to say much without seeing it though.

 

heres about as bad as it gets. it wont come off anytime soon but its clearly not right.



and heres when i push it in. looks ok.

 

One of the clips holding the bumper is probably bent down from the crash, which lets the bumper slide out over time. I would maybe remove a few screws from that side of the bumper, and just pull it out a little to see if a clip in bent. It should be where that cut out box on the bumper is in the first picture.
The bumper is plastic so you should have some room. If it is just push it back up, reinstall the bumper and you should be good!