I have noticed this same sort of thing after i took off my Invisible Shield screen protector. I don't believe it is a surface scratch since the glass is is smooth and even throughout the area. Upon looking at it from different angles I can be 100% assured that it is from the inside. It looks like small groupings of bubbles which I thought was the glue keeping the display together coming apart. I was planning on going in to an Apple store with this but I don't want a refurb after all the problem's I've heard people have with them. For the most part the phone is flawless

Other than the weird bubble phenomenon
I have also attached a picture of what this is (i tried my best given my camera and lighting conditions)