Is testicle inflammation from over masturbation dangerous?

What do you mean?: If you're sore from your equipment getting roughed up during vigorous activity, figure out a way of getting better support. Pain from prolonged arousal is best rx'd by ejaculation by whatever means. If you have ongoing tenderness / pain in the epididymis, get with your physician for probable epididymitis. If you have severe or lasting pain in a testis, get seen by your physician.

Inflammation?: Masturbation doesn't cause testicular inflammation. If your testicles are inflamed, get checked. It might be something you picked up from having sex with someone other than yourself!

Not related: Unless you're hurting your testicles during masturbation, which some men do, there is no relationship between the two.