What can cause testicular/scrotal pain?

Many things.: Acute scrotal pain can be caused by testicular torsion, infections such as epididymitis, orchitis or mumps, appendix testis torsion, cancer, hernia, hydrocele, spermatocele, varicocele & traumatic injury. If you have sudden pain, please see a physician since torsion or infection must be treated immediately. A physician will be able to assess the need for scrotal ultrasound & direct treatment.

A variety of things : Torsion, tumor, infections (including std, insect bites, exposure to mumps), trauma, varicocles, iatrogenic (secondary to procedures), hernias, to name a few. Hope this helps.