J.K. Rowling wrote fairly extensively about Harry's scar hurting when Voldemort was feeling certain emotions or when there was a mind connection between Harry and Voldemort. Why, though, did Harry experience pain in his scar, rather than throughout his body as a whole? What was the significance of the pain Harry felt in his scar? If it weren't important, I don't think it would've been such a theme throughout the books; however, none of the books address why Harry has pain in his scar or what the significance of the pain is.
ETA: Please no HP Wikia answers.