What Causes Pain In Lower Abdomen Radiating To Rectum?

I am 69 years old and had lower abd pain with radiation in to the rectum. Had an US than a MRI. The MRI find a Bilobed cyst on the right ovary cyst. I was told not to worry and repeat with an US in 2 mths. ? should I be worried because of my age. Or should I just repeat the UN as advised. No family history of ovarian CA but many other types of CA. Thank you, Di