Awkward erection in wrong situations, what to do?

Manage it. Every boy learns around the time of puberty about how to conceal an embarrassing erection. Put your hands in your pocket. Button your jacket, pull down your hoodie, keep the thing pointed upward and in the midline. Skip the shower. Adults know and don't care. Enjoy your body to the point of ejaculation as needed to stay able to keep your mind on other things. Enjoy being fit and male.