Need some help; screen issue

[WeAreAllUnique]

Somehow, my Nexus 6 screen has a weird blemish on it. I don't know how to fix it. It won't show in pictures but it looks like a faint watermark. It's more noticeable when the screen is smudged. Anyone have any ideas?

 

[SactoKingsFan]

Might be screen burn in.

 

[WeAreAllUnique]

It's not screen burn in. It's on top of the screen.

 

[WeAreAllUnique]

Did some research. I'm not sure but it could be that the oleophobic coating has worn off in that area on the phone. I don't see anything when the display is on. Screen is perfectly clear. But when I turn the display off I can see it if there are smudges on the screen. When I wipe the screen completely clean I see nothing again.

 

[WeAreAllUnique]

So I ordered a tempered glass screen protector. Put it on and cannot see the faint watermarks anymore. I'm convinced it was the coating.