Im 20 years old and had a ct scan for a kidney stone at the hospital and they found a incidental 11 mm interpolar left renal cortical cyst should i be?

Renal cortical cyst: Very small cysts might cause no problems at all, and you might not know you have the cyst until it is found in a routine examination for other issues. As the cyst grows larger, you might start to feel pain or pressure in your back or sides, which often radiates downward. The pain is usually dull, not sharp. When it becomes big enough, you might be able to feel it when you press down on your abdomen. You might notice blood or bubbles in your urine. You might also begin to experience problems with high blood pressure.

This is a: common incidental finding. The vast majority of renal cysts never cause any symptoms or problems, and require no treatment.