hmm you could go to a body shop and see what they think. but it doesn't look to bad. some of it looks like surface rust which can be sanded down to bare metal and painted. if it is bad you could also just get as much of it sanded off, use some body filler and be paint over it but the rust will eventually come back.
the good news is its in a relatively conspicuous place so whatever you do to fix it odds are it won't be noticeable. bad news is I bet if you remove that side skirt I bet the rust continues there as well.
biggest thing I can tell you is to watch your rear wheel wells where the bumper connects to the body. idk how many people on here (myself included) have gotten rust bubbles started there and that is a place where it is very visible. as soon as you see any sort of rust in that area get it taken care of asap! rust really is a cancer for cars and will continue to grow unless you fix it.
