Pain in the testicle can have multiple causes including infection in testicles, cancer of testicle,infection in epididymis, varicocele, epididymal cyst hernia in groin, pain from muscle strain in groin or referred pain from prostate problem. Ultrasound scan will only rule out infection of testicles, cancer of the testicles, epididymal cyst, varicocele and some other conditions and not all. Please see your urologist for further evaluation and detailed examination for the cause.