On the first day God said let there be light , right?

Yes, you are missing something. The sun, moon, and the stars are indeed all sources of light. But light itself was created on the first day. In the book of Revelation in 21:23, 24, the sun, moon, and stars are all gone, but there is still light.

God Himself is light. In Him is no darkness at all.... 1 John 1:5

You are getting tripped up by the assumption that you have to have the Sun, Moon, and stars to have light. The Bible says that God is light. Also, God doesn't need the Sun, Moon, and stars to create light. This verse is probably referring to the creation of electromagnetic radiation, which would include visible light.

If you are looking for insight, then look away from the bible, read a better and more cleverly crafted story like Harry Potter or something

imagine light was a big, vast horizon of nothingness, just the color white all round. like a brand new piece of paper.

the book of genesis is not meant to be taken literally. its a story passed down through generations to teach people of God and what happens when you sin against him.