It's a common myth that nicotine can cause testicular pain, but there's no evidence to support this. In fact, studies have found that smokers are actually less likely to experience testicular pain than non-smokers. So if you're a smoker and you're experiencing testicular pain, it's unlikely that nicotine is the cause.
There are many other potential causes of testicular pain, including infection, injury, hernia, or varicocele (enlarged veins in the scrotum). If you're concerned about any type of pain in your testicles, it's important to see a doctor so they can rule out any serious underlying conditions.