My Left Eye (only) Socket Hurts When I Blink. At

My left eye (only) socket hurts when I blink. At first, it only hurt when I touched, like pushing my glasses up, but now it is pretty constant and a sharper pain when I blink and with movement of the eye ball. My actual eyeball is starting to feel strained as well. It is most painful on the bottom of my socket, however, the upper brow bone area is painful to the touch. Any suggestions as to what it could be?