Last night my girlfriend and i had unprotected sex. During sex i felt a sharp pain on my penis but it went away a little after. I got home and i noticed my penis is cut under the head when pulled back (im uncircumsized). is this a serious injury or not? we had sex during her period so it was messy and i thought all the blood was that tho i dont think it was me but i had that cut. i didnt ejaculate at all aswell. also with all that blood can it affect the sperm?