No one has ever seen God, but God the One and Only, who is at the Father’s side, has made him known.
“No one has ever seen God” with the physical eye. God is spirit and invisible. All of man’s visions of God were partial until Christ. (Ex 33:20, De 4:12, John 6:46)
Exodus 33:20 But,” he said, “you cannot see my face, for no-one may see me and live.”
Deuteronomy 4:12 Then the LORD spoke to you out of the fire. You heard the sound of words but saw no form; there was only a voice.
John 6:46 No-one has seen the Father except the one who is from God; only he has seen the Father. )
“God, the One and Only” is translated in KJV as “the only begotten Son”. RWP (and other sources) state, “the best old Greek manuscripts (Aleph B C L) read onogenes theos (God only begotten) which is undoubtedly the true text.” This may have been changed at a later date by a scribe to make it less blunt and more like John 3:16. In its original form, it is another and bolder statement of the deity of Jesus Christ. Jesus is God.
“at the Father’s side” denotes unity of nature, distinct personality, sharing of love between Father and Son, and close proximity between the two. Jesus is so close to the Father that He is at His side or “in His bosom” (AV). This imminently qualifies Him to reveal the Father to us; Jesus is the closest to the Father, and thus the best possible revealer of Him. We can have confidence that God is as Christ has revealed Him.
Jesus “has made Him known.” How did He do that? By showing us Himself.
John 14:7 If you really knew me, you would know my Father as well. From now on, you do know him and have seen him.”
The prologue ends with this verse and rightly so since here “the Logos is pictured in marvelous fashion as the Word of God in human flesh, the Son of God with the glory of God in him, showing men who God is and what he is.” (RWP)