St. Nicholas of Myra lived and acquired his reputation for sanctity long before the Church began its formal process of beatification. He became recognized as a saint by a kind of popular acceptance.
Historians and hagiographers generally write that much of what is said about Nicholas is legend. Again, remember that at Nicholas's time there were no investigation and authentication of claimed miracles before canonization took place. Attributing miracles and wonders to a person was an ancient way of expressing people's conviction about the holiness of the person.
You will still find Nicholas listed in the various dictionaries of saints, for example, Dictionary of Saints, by John Delaney (Doubleday). And you will still find Nicholas listed in the Roman Calendar on December 6. There he is assigned an optional memorial.