The phrase "infinite and eternal" really indicates that it is beginningless. He always existed, people changed him, Lucifer and the history of creation with their dreams. In Lucifer Vol 1, there are creators before him, but since he is infinite, his true self is one with the Void, and the dreams deemed him worthy of Godhood itself. Stop talking about creation as the physical world, you're practically declaring that you haven't read the series.
This is confirmed by official sources
In the nothingness after what came before, a power later
known as both the Source and the Presence sparks
the Big
Bang that creates the universe. Attempts to study creation
by a future scientist named Krona interfere with the mo-
ment of creation, shattering what would have been a sin-
gle universe into a multiverse, as well as a parallel antimat-
ter universe. Tachyons projected by Krona create entropy,
evil, and chaos where none would have existed, through
all of eternity. The newly divided light and dark aspects
of the multiverse become personified with the creation of
the Monitor and the Anti-Monitor, powerful beings of the
matter and antimatter universes whose conflict lasts until
the present era.
In the beginning, the Presence created the universe, push-
ing back the primordial darkness to the fringes of creation.
From the resultant chaosplasm, the Presence created first
Heaven and then the
physical structure of the multiverse.
For most of history, those that believed they
knew the most about the Source Wall in Earth’s universe,
The New Gods, thought that the wall provided a sanctu-
ary behind which existed
the Source, a cosmic conscious-
ness they equated with the Presence or the creator entity
behind the cosmos itself.
The truth of creation is unknowable
Though the full truth of the time before the beginning of the universe is unknowable, there are events that are said to
have occurred. The New Gods of Apokalips and New Genesis tell that this was the time of the First World and then the
Second World, when the Old Gods of the Godworld watched over the adventures of the first hero, Aurakles. During this
period, the first of the forces known as the Endless also came into being.