Left testicle hurts and my left flank hurts?

Kidney stone. Pain in the left flank and left testicle may signify kidney stone disease. This is referred pain from trying to pass a kidney stone. You need a urinalysis and possible x-rays to help diagnose. See your local urologist.
Could be a stone. This specific set of symptoms *may* be caused by a stone. I would suggest evaluation by a physician to examine you and check a urinalysis and an imaging study, such as an xray, ultrasound or ct scan of the abdomen and pelvis. Other causes can be determined if no evidence of stone is found.