White Blotch on iPhone 5C

I just bought a used iPhone 5C on Amazon. It's in very good condition, except for this white blotch on the screen. It doesn't seem to be from pressure (I pushed on it and the color didn't change) or moisture (I put it in rice to no avail). Does anyone know what this is or how to fix it? It sort of looks like an explosion, and it goes from the top of the screen to about the middle. It doesn't affect the usage of the phone. (I tried to attach a photo but it didn't work.