How long ago was this? If you just had sex and then spotted the next day I would say it was from the rough sex. If your period is late, or if you had sex around the time you think you would ovulate...then you might be pregnant. Only way to tell is to test.
It all depends on what part of your cycle you are on. I found that the closer I was to ovulation the more sensitive my cervix was and sometimes I would have pink spotting after sex.
if your late then i would say test, if not then wait for a few more days then test. good luck hun.