Weird random patch of colors on iPhone 11 screen.

Hey,

I just noticed that my iPhone 11 screen has a small patch of weird colors stuck there, ranging from green to purple. They don't go away, and it doesn't look like it's a software problem since I tried screenshotting and it's not there. The patch of colors are mostly visible when my iPhone is on dark colors, and it is basically invisible when it is on bright/whiteish colors. I uploaded a picture of what it looks like when put on black.

Any idea what it might be?