Ultrasound showed 2.4x1.3 cm hypoechoic nonvascular region in upper pole cortex of left kidney. Otherwise normal kidney. I'm freaking out. Cancer?

It can be benign. Cysts are common in the kidneys. So ask your doctor to confirm if it is cystic or solid structure. Cysts are benign fluid filled structures whic can be left alone. Solid lesions can be a tumor and may need to be removed. Repeat follow up in 6 months can be reassuring if there is no further increase in size. You may need to seen a Urologist to advice you further.