In John 1, we read Christ is the light of all.
John 1 v 4-5
In him was life, and that life was the light of all mankind. The light shines in the darkness, and the darkness has not overcome it.
The Genesis 1 Creation narrative is confusing, as light seems to be around before the Sun and stars. However, this light, which brings understanding, is not from the Sun, but from God.
Christ is the Light of the World. Not the material light from the Sun and stars, but the light by which reality can be comprehended.
Christ is the Uncreated Light. He comes from outside of Creation and incarnates on Earth.
He is like someone walking into a room with a lantern, lighting it up. And revealing all things.
Equally, when we welcome Christ into our inner World of thoughts and emotions, we see ourselves more clearly. He is the reference point by which we can understand our thoughts, desires and motivations.
He also comes into our communities, helping us to see the failures in our relationships and helps us to fix them.
He even brings light into the darkest parts of his Creation, Hell itself. After His death, He harrows the Underworld, freeing those held captive.
At Christmas, the light by which humans can comprehend reality, incarnated on Earth. As we look to His light, He shines around us, in us and through us. And so by Him, we see all things more clearly.
Thank you for introducing this discussion. The biblical days of creation, especially the first few, describe, for people of all times through history, events and processes that we really cannot comprehend. I stretch to even picture in the abstract whether time itself spread through the material mass-energy universe, or how the universe as we now observe it came into its present form. The symbolic Big Bang also tries to explain what happened, but the whole space-time-matter-energy continuum was just forming, so whatever description we have, as true as we believe the biblical account to be, IMO can be little more than an allegorical description of things we are incapable of understanding. We can call it theoretical physics, or cosmology, or magic, but as you suggest, the light God spoke into existence did not have to come from things we think we understand today, like stars or suns. Then comes the biblical claim that this Light came into the world that was made through him yet knew him not. These are not petty thoughts!