I would advice you to get another ultrasound
done to ascertain the exact nature of this ovarian cyst
. If your friend thought it to be something serious, I would think he would have communicated it to you.
However, it is better to put your mind at rest. Make an appointment with your gynecologist and mention about the previous finding. Once they have done another ultrasound, and if need be, blood tests, the picture should be clear.