I was diagnosed with cyst inside my ovary in january it was 5cm then ultrasound scheduled next one is 3 month away. will i need surgery??

Simple cyst: As long as the cyst is described as a simple cyst (round or oval shape, smooth thin walls, no solid component or septations, and no blood flow) it is almost certainly benign meaning that surgery is not likely. If your cyst is not simple and it does not get smaller on follow-up, it may require surgery to remove the cyst and make sure there is no evidence of cancer.