Child age 5 kick to testicles, pain gone in 5 mins, no swelling/bruising/bleeding. can you confirm this will not reduce sperm production as adult?

No...but unlikely: The adage never say never applies in this case.Males routinely experience simple trauma to their scrotum/testis that varies in intensity.Testes are surrounded by fluid & tissue layers that absorb some of the trauma.They can lose the function of one & still be fertile. In more than 3 decades as a pediatrician I have never seen or read of a kid losinge one or both of their testis from such trauma

Very unlikely: If there was no injury to the testicles; this is not something to worry about. All the best.

No worries: Will be fine. No long lasting effects.