oh yeah sry brainfart i meant joyboy
I dont think we have 100% confirmation nika was even real at this point, could still be a fable/dream people "willed" into existence
I think there was a first Nika, and I actually do think Oda will show him, but he's not individually important to the story.
Ever since we were introduced to the Mother Flame as some kind of nuclear energy source, I've speculated it had something to do with the origins of the Devil Fruits. Then the Harley lore dropped and it appeared the First World was one of deep inequality with those on the top reaping the benefits of those toiling below.
Nika was introduced as a warrior of liberation, i.e. a breaker of chains and saviour of slaves, who would come in response to wishes of the oppressed.
If you pair that with Vegapunk's speculation Devil Fruits are borne out of wishes, and then further consider that the Mother Flame might have something to do with it, then I think it's very possible the first Nika was a slave of the First World that, perhaps, fell down so far below he was all but dead until he found the source of the Devil Fruits, bit in one to survive, and the First World became history.