Yes I Recently Had Testicular Pain And Went Too The

Yes I recently had testicular pain and went too the E.R. They did an ultra sound and found an epididymal cyst and referred me to an urologist, but my appointment isnt for 3 weeks, and im worried sick it could testicular cancer. Can an ultrasound distinguish between cancer and a cyst even if it was done at an E.R room and should I be worried?