What can i do if my testicle is swollen and tender, hurts! please help?

Needs 2B X'd ASAP: Sudden onset pain & swelling of testis is torsion untill proven otherwise. This is an emergency & warrants an er visit 24/7 as there is risk of testicular death after 4 - 6 hours, and certainty after 12 hours. More common at your age would be epididymitis, bacterial +/- UTI or viral & treated with antibiotics & rest. Less common is testis tumor + hemorrhage. Scrotal ultrasound can distiguish.