The best thing to do is to check with you primary care doctor.
Here is what the CDC says to do:
COVID-19: When to Quarantine | CDC
Some bits of what the CDC says
"Quarantine is used to keep someone who might have been exposed to COVID-19 away from others. "
you should quarantine if "You were within 6 feet of someone who has COVID-19 for a total of 15 minutes or more"
There are more details but since the person tested positive I think you have to assume that they have been exposed to someone who might COVID and so might have COVID. So it you were near that person you probably should quarantine for 14 days.
But read what the CDC has to say for yourself.