I want to say that's not true Elfie. Watched a documentary on McNamara a couple of months ago and he said that Fidel confided in him later that soviet nuclear armed tactical weapons were on the island.
I think Soviet advisors were always on the island, I kinda doubt that the Soviets would put those nukes under Castro's control. (Which is the only way I would say Castro had nukes.) I feel reasonably confident those nukes were always under Soviet control.
Otoh, that is something I didn't know. Very interesting as well.