In John 20:28, Thomas is quoted by John in addressing Jesus as" my Lord & my God." The New World Translation reads the same. John makes no attempt to explain what Thomas said. Since nobody living today was there, none of us are in any position to infer, interpret, dismiss, add-to or minimize Thomas' words. John accurately conveyed the exchange and all translations have accurately rendered that verse.
So now we'd need to ask "why?" Why did John recount that and many other events? Most people I meet would say that the reason John wrote that was because he wanted his readers to believe that Jesus is God. However, John doesn't leave his readers hanging. In verse 31 (a mere 3 verses after verse 28 where John quoted Thomas) John does explain why he wrote his whole gospel account. There he says, " these have been written down so that you may believe that Jesus is the Christ, the Son of God."
If John had wanted to prove that Jesus was (is) God, you'd think he would have stated that very plainly--instead of what he wrote in verse 31.