Take a deep breath... I know, more easily said than done.
Ovarian cysts are common and are almost always benign / non-cancerous (including large ones). Most resolve on their own, no intervention needed. However, yours is past that point due to its size so will need to be surgically removed. If the frozen section done at the time of surgery is benign, a surgeon with good cystectomy skills should be able to remove just the cyst and save your ovary or at least most of it.