And you are sure this is not your period coming a bit earlier or restarting shortly after it stopped? Sometimes this happens and the better the orgasm, the more likely it is to happen.
A cut in your vagina is no different than one at any other place. After 3 days it is however time to call your doctor (just like if you had a cut in your foot or lip that bled for 3 days). Normally rough or nonconsensual sex damage the soft area between the vagina and anus (perineum). This area is easy to tear and it will sometimes tear during childbirth. Stitches may be necessary to make it heal. Did you take a mirror to see what happened?
You can try Ibprofen (an NSAID pain killer) for it's anti-inflammatory action as well as the fact that it thickens your blood. Follow the instructions and do not overdose. An iron supplement canals do you good and give you some energy back. Once again, do not over dose.