I have symptoms of pain in the left side back / front top of left abdomen - near left rib . had a cat for diverticulitis "simple cyst at left kidney upper to midpole posteriorly measuring 13 by 8 mm." could that be causing the pain? it is sever?

The cyst of that size rarely causes any pain. Simple cyst is very common at your age and it is almost always asymptomatic.

It is not likely that the cyst is causing you the described pain, further work up will be needed in order to properly assign your pain to its cause. Many times the cause is musculoskeletal and hard to determine with imaging studies and that’s why is important to keep a log with circumstances that trigger the pain or alleviate it, for example, as any such information can be used by your doc.