Sorry to have missed this Monday!

(Thank You for the PM reminder - busy time of year and I
do miss things I could respond to!)
Which came first, the chicken or the egg? (it was the egg, but that's not important here) Whatever the cause, this is above the water line and isn't a leak issue while running the pool at a normal level

However, I understand, and agree, with your concern in not letting the rust damage continue to the point that it could cause a leak!
To address this you need to remove the faceplate coverplate (I've never been able to do it without wrecking the coverplate

, lower the water and remove the sealing faceplate to inspect the damage. The damage may very well be to the wall panel itself, which would require a good bit of work to repair. How much deck do you have there? It's possible to tunnel under the deck to replace the skimmer (gaskets). What I would do, for at least this season, is to use 2 part epoxy on the inside of the skimmer mouth to keep water off of the panel and then think about buttressing the panel and putting on new gaskets.
I'll tell you about any step in this when you decide how you want to tackle it 8)