If it’s a few days after ovulation it can be implantation bleeding. If you don’t get your period I would take a pregnancy test.
If you start having constant spotting I would go to the doctor ASAP. If you get your period and everything goes back to normal I wouldn’t worry. If it happens again probably make an appointment. I think a day 3 test would be good, but they might want to do something different. Maybe you are having something go haywire in your luteal phase.
I’m just telling you what I would do. I’m not a doctor.