Hello I am a 20 year old female. I am experiencing spotting after having vigorous sex (rough sex) for 2 days now but I am not feeling any pain, what might be the cause of this? How long will the spotting last?

Hello I am a 20 year old female. I am experiencing spotting after having vigorous sex (rough sex) for 2 days now but I am not feeling any pain, what might be the cause of this? How long will the spotting last?