you should get yourself check by a doctor.Their can't be any serious issue as i see but certain minute complications are possible
This situation is hard to give advice on. It could be caused by several things, and can't be for sure without further testing and observation from a physician. It could be caused by irritation or infection. It could be caused by irritation from aggressive or rough sex. If your partner's penis is larger than you are used to, it could cause small tears within the vaginal walls and this would produce blood. It should just be spotting, and not enough to saturate a pad or tampon. If it is a large amount, it could be a hemmorage. You should just keep on eye on it, and if it continues, gets worse, or because a problem...you should see your doctor.