I had this happen to mine too, but I found the problem.
It's because the bracket that's holding up your bumper is not screwed into your taillights. When you went to take off your taillights, you probably thought those screws were unneccessary, but they're actually what holds the brackets up. Without those, your bumper will start sagging, and that part on the side will stick out like you said.
one of the clips that holds the bumper must be broken, mine broke after a fender bender and the shop "fixed" it, when i went to take the bumper off to replace my taillight gaskets i had to unscrew a fucking rusted screw that was holding the bumper right at the seem, fuckers didnt even put back the screws that go under the tail light :firemad: