How to get a speck out of my iphone 5 camera?

I have the iphone 5 and i have like a really good otter box on it but yesterday i found a small purple spec on my camera. Its weird because the speck doesn't appear on the front facing camera. I don't know what to do about it either its so annoying too. Other than going to the apple store what can i do? Anyone?

I would try cleaning the surface of the camera, because sometimes the otterbox cases press dirt on the phone. If it doesn't work, then go back to the Apple Store, and demand a new phone, because it may be a defect.