What Causes Pain And Swelling In Elbow?

2 or 3 days ago my elbow started to hurt a bit, and as time as gone by it has started to swell a bit. I got something that looks a bit like a mosquito bite or a zit at the tip of the elbow and it is really hurting as of now.
It doesnt just hurt at the supposed "sting" but around the entire area of the swelling, what might this be and what should I do about it?