Arm Rash/Tight Painful Skin

My arm has been bothering me for a few days now. Right by the crease of my blow on my forearm, the skin feels extremely tight and awkwardly painful. Occasionally it tends to itch a lot and then the rest of my arm begins to itch as well. However, there are also some very lightly colored blotches under my skin from the crease in my elbow down to about 2 inches above my wrist. When my arm is flexed, the pain ceases for the most part. But when I extend my arm to stretch and what not the pain is ridiculous. It's like a burning/ripping feeling under my skin. What could this be?