Xperia Z3 :: Small White Mark In The Middle Of LCD

I recently noticed that there was a lighter white mark in the center of the LCD screen, no larger than a grain of sand. It isn't a dead pixel but when the screen displays bright colours like white, cyan or yellow, I can clearly see a white mark. It's not very noticeable but I know it's there which is quite irritating. I doubt it is worthy of a replacement but it's worrying as I assume it is the components behind the screen pushing against the display. I don't know of it isn't any relevance but I noticed this after my screen was replaced for free by Sony after a different issue.