What Causes Raised Darker Patch Of Skin Along Upper Lip Lining?

I am a 31 year old male. I have a slightly raised darker patch of skin along my upper lip lining. Every now and again I will get a very small pimple along the same location. It is not painful at all, and barely noticable. The edge of my lip does not seem to be as distinct as it should be. I just want it to go away.