I just saw these blue/purple spots underneath my lens (attached here). This is a Nikon D90 which has the Nikkor 18-105 mm lens mounted on it. I haven't used it for maybe 2 months now, and I kept it inside my wardrobe in the camera bag.
I'm wondering what caused this to the lens. Should I be worried? Is there any way to clean it up? Will this spread inside the lens?