How To Get Rid Of Dark Mark On My Nose Pad Due To Spectacles?

I used to wear glasses for for few years. At that time, I didn't had any darak mark from the nosepads. I am not wearing since the mid of 2009. But after stop wearing it, I started noticing the dark mark or bruise on the nose pad area. It became more darker when I am tired. Why is it happening? Is it a bruise from the nose pad? or is it somethingelse? How can I get rid of it? Thank you, Anna