Have you ever had shin splintz? This is basically the same thing, but in your forearms. Certain exercises give me these - straight bar curls, reverse grip curls especially.
I'd take a week off and relax. Use the EZ curl bar for all curls instead of straight bars, or better yet use dumbells. You could also increase rep range.
Many people who complain of this are guilty of relying too much on straps. Since I've cut back on straps (I use them only for shrugs and deads) I've eliminated any potential pain in this area.