Don’t humor your OCD. If your phone has an incredibly minor defect but is perfect otherwise, do not exchange it for another one as you could end up with an actual lemon. I’ve seen paint come off the rear camera housing after a few months which is not covered by Apple due to it being a minor cosmetic defect. I have also seen paint flicking off some phones through no fault of the owner. These are cosmetic defects that are common to iPhones. A tiny speck on the back of an iPhone is not even a defect as it’s such a minor imperfection. Even a single dead pixel is not considered a replaceable defect by some manufacturers, but that probably would bother me.