I have had this problem for about 9 months (maybe longer). It never appeared to degrade the images taken with the camera (I'm not a looker anyway). When I was in the local Apple Store 6 months ago, I looked at a display iPhone 6 and was surprised to see that it also had the same problem.
Checking online I found others reporting this issue.
In the end, before my warranty ran out, I took it in and was immediately given a replacement phone. I strongly suggest others do the same they lose their warranty coverage.
My new phone's camera looks very different, almost identical to my iPad Air 2.
Apple should be acknowledging what is an obvious design flaw or manufacturing fault, so that effected owners can get replacements after warranties experience.