You want a transvaginal ultrasound and a CA-125 bloodtest to rule out
ovarian cancer. I know nothing about
ovarian cysts, but they are much more plentiful than ovarian cancers -- and almost always benign -- so try to "think positive."
If, after examination, your gynecologist suggests that surgery might be in order (even for cysts), please be sure you get a gynecological oncologist (who will have several years more training and is a specialist in gyn surgery) for the surgery.