My balls aren't smooth. I started puberty. What does that mean? (age 10)
I assume you are referring to your scrotum (the sac underneath your penis) and not your testicles, which are in your scrotum. The scrotum is not smooth because it's job is to keep your testicles a degree or two cooler than the rest of your body. When you get warm, especially when you get a bit older, the scrotum expands and hangs down. This exposes more skin surface to let heat radiate from the area. When you get cold, it scrunches up, making the walls thicker and so there is less surface area for heat to escape.
Now, if you are actually referring to your testicles, then you need to describe what you are feeling.