I sometimes pull on my penis or yank it to keep it kind of active and one day i tried stretching it a little bit and ever since then a vein on the top part of my penis hurts when i am erect and push my penis down to stretch the vein..im worried that wen i have sex it will hurt but i never had any serious pain only if i push down alot, no blood, no signs of injury just the slight pain.. what should i do?