6+ scuffed screen - almost appears to be under the glass

Usual caveats: I look after phones well - never in a bag, always the only thing in my pocket etc.

My day one 6+ has been in an apple (red) leather case at all times.

A while ago i noticed a finger print smudge that wouldn't clean off with a cloth.

it almost appears to be under the glass - like a milky, scuff mark. (see image)

anyone else had these issues. I've lived with it for a while now as its on the bezel, top right not on the screen area

but its starting to annoy me.