I would call the obgyn to be on the safe side and see what they say. I had that happen to me recently where I had light spotting for one day. I called the doctor and he said if the bleeding continued, became heavier, or the cramping got worse (I had light cramping) to go to the E.R. But that everything was probably okay, and to try not to worry. It stopped, so I think everything is fine. Apparently it can be caused by implantation bleeding, sometimes by sex, or unfortunately could sometimes be a sign of a miscarriage. So I think it would be best to let your doctor know and see what they say to be on the safe side--but everything is probably okay.