I'm 22 and I have solid ovaries

A year ago I found I had a cyst in my ovaries, then the doctor told me not worry about it. Fast forward to this year, I had alot of lower abdominal pain, went back to the doctor, they cyst has grown. I was put on 3 month medication- a painkiller and 21 day pill.
Went back for follow last week. My cyst is gone.
But both of my ovaries. Can someone tell me why?