The New Testament applies divine language and worship to Jesus. Around the beginning of the second century Ignatius can write, ‘our God, Jesus Christ’ (Ephesians 18). Pliny the Younger, a Roman governor hostile to the movement, reports Christians singing to Christ ‘as to a god’ around A.D. 112. Justin Martyr calls the preexistent Word God, and other pre-Nicene writers defend Christ’s divine identity in different vocabularies.
The Council of Nicaea answered a real controversy about how the Son is related to the Father and confessed him as true God from true God, of one essence with the Father. The council’s technical precision mattered. But the worship and divine status of Jesus are embedded in sources centuries earlier.
Primary sources
Ignatius, Ephesians: https://www.newadvent.org/fathers/0104.htm
Justin, First Apology: https://www.newadvent.org/fathers/0126.htm
Pliny, Letter 10.96: https://www.pbs.org/wgbh/pages/frontline/shows/religion/maps/primary/pliny.html