What is the Council of Nicea anyway? Well, it was a conference called by the then Roman emperor Constantine the Great in 325 AD for all the bishops to settle their differences regarding the deity of Christ. One of the bishops by the name of Arius (c.250-c.336) said that Jesus was not of the same being as God and therefore not God but the highest of creatures, created by God for a mediatory and creative role.
Arianism was condemned at the council of Nicea and the view that Jesus Christ is truly God and is of one being (homoousios) with the Father was affirmed.
Sad to say, some form of Arianism or semi-Arianism continue to exist to this day.