Looking for an app that darkens part of my screen – any suggestions?

Before I start, I want to say sorry if I’m my thread is not what this forum is aimed at. I found people making this type of threads so I decided it’s worth the try.

So, I got a screen burn-in which is a hardware problem, I know. But I think that if I find a background app that darkens that part of the screen, everything would be fine and it won’t be noticeable. The burn-in is still there, but hidden. Problem is, I can’t find one that does the job. Any suggestions?