I am a18yrs old girl,I got severe stomach pain and swelling in the stomach,as per scaning result presence of a cyst in the overy,is this the exact reason for pain and swelling

This is something you should be telling your doctor. No way for anyone on this site to know if the pain is due to the cyst, something you ate, illness, menstrual cramps, nerves, or anything else.

No one can diagnose online. If you're having issues, seek medical help.

Good luck.