iMac Screen chipped?

Recently I noticed a slight spec on the screen of my aluminum iMac, and it looks like it does when a drop of liquid hits your screen, all color-changing and stuff. It would not wipe out with a damp rag and I'm not sure what to do. I haven't moved my computer around or anything so there should be no reason for this "chip". It is very miniscule but it drives me nuts because I'm a perfectionist. Does anyone have a solution to this problem?