I have a growth underneath my skin under my scrotum is it just a pimple to pop or is it cancer?

Not likely to: Be cancer. Don't pop it, but you can soak in warm water in a tub and use soap. The adjacency to your rectum, not the cleanest part of your body, makes "popping" a bad idea. See a doctor to make the call and do the dirty deed if needed.

Probably infection: Abscess are more common in this area than cancers. Apply warm compresses to the area and if does resolve or worsens see your primary care physician.