Ultrasound says 9mm small renal cyst, was not indicated if its simple or complex. What will I do? Will I repeat it again? Pls help

Most Likely Benign . Most sub-centimeter cysts are too small to further characterize. However, if the radiologist didn't mention anything complicating the cyst, than its most likely simple and requires no follow up. Many people have simple renal cysts and this is a very common incidental imaging finding.
Repeat. Have a sonogram repeated again in 3-6 months to see how its growing. In majority of cases such cysts remain the same.