When God said "light be" it had nothing to do with physical light, as it was not until day three that God set the stars and sun to shine upon the earth, and its purpose was to measure time, seasons, and days.Amen and so since "time" (Chronos) began at that moment one cannot rightly speak of a "before". There was God, and whatever was created...timelessness was...then when God said let there be light there was light....bereshith...
Human language and ability to cognitively conceive is too limited to actually grasp it...
Gen 1:14 And God said, "Let there be lights in the expanse of the heavens to separate the day from the night. And let them be for signs and for seasons, and for days and years,
The New testament gives us insight into what the Lord God was doing when he said "let there be light"
2Co 4:6 For God, who commanded the light to shine out of darkness, hath shined in our hearts, to give the light of the knowledge of the glory of God in the face of Jesus Christ.
Haven't you ever wondered when God caused his grace to appear unto all men?
Tit 2:11 For the grace of God that bringeth salvation hath appeared to all men,
God was shining his light throughout all time into the hearts of all men that would be born on planet earth so they could be saved, and not have any excuse because God has shone it to them from the beginning.