Your bow arm forearm appears to be correctly aligned, so if you hit it with the string after making the adjustment that Arne recommends, you should probably wear an arm guard. Your forearms are well developed, so it may be inevitable that you will hit them when you shoot the bow correctly. Any little sting you feel, whether it's the string hitting your nose or your forearm, is a distraction that will take away from your concentration. Even before Arne's correction, your form is good enough that I suspect your greatest improvements will come from increasing the mental aspects of your shot, primarily your concentration.