Im a newly 16 year old boy, i have had an aching pain in my left testicle for 3 days now. my scrotum is not swollen it just aches and im scared.

Don't be scared!: Testicular cancer is unusual at 16, doesn't usually cause pain, so this is unlikely to be dangerous. If the testicle is hard, irregular, or enlarged, should be examined to rule out unusual tumor or malignancy. Infection or epididymitis usually causes severe pain, swelling, redness. Most common cause of aching in an otherwise normal testicle would be a varicocele - pain when upright, better lying.