Swollen outer corner of left eyelid?

Hello everyone :) Well... I woke up yesterday (Monday) morning with a sore pain on the outer corner of my left eyelid on top. It just started out as an annoying pain but then today it has gotten worse. My left eyelid near the outer corner is now swollen & pinkish red, sore to the touch, hurts when I move my eye to look around or blink. Why would it be doing this randomly??? I've never ever had a sty or pink eye and I haven't ate anything or done anything out of the ordinary so I doubt it's an allergic reaction to something. The pain is just getting so annoying and my upper eyelid is getting so swollen that it looks like its drooping just slightly over my upper lashes, but not enough to interfere with my vision. Oh and I'm not having any other problems with my eyes like vision, I don't wear gles or contacts, and I'm not sick or anything at the moment..... this eye thing is all! I just wanna know what it could be or could it be reason to see a doc!!!?