Momo has had this dent as long as I've had the car, and you can see a rust bubble on the edge of the bumper trim.
I beat the dent out with a hammer and dolly, and patched it today
Along the way I also cut out a bunch of rust. I didn't do a perfect job but I got the bulk of it. I might come back to it later. The white paint I had didn't match the paint on the car very well so I'll go have another can of colour match done and put a few more topcoats on.
Here's some photos of the process. The car seems like it's had an impact on this corner at some point in the past.
To avoid a seam along the chrome strip, I punched it out from inside the boot just enough to make it lift away from the paint but not so much that I'd have to replace the trim clips.
