It may depend where you cut it off if we have to consider nerves, nerve regeneration is hard but grafts are feasible. Equally reattachment is a possibility in some cases. Are your testes going with it in this hypothetical?
Stem cells grafted over a framework would probably be the first time where it is feasible for going from scratch.
With all this said though you still have the existential question of is it your dick? Cell renewal is a red herring debate -- it is not the one you presumably spent good times with before now.