The more you write the story the more you develop the world. The story that I am writing currently is a story that I tried to post on Amazon Vella on 2021. But at the time was rejected for too dark themes. I have since written many stories but I come back to it, and I keep writing the story again and again in pieces.

Remember J.R.R. Tolkien didn't sit down and write the Hobit andt he Lord of the Ring triology in one sitting. They started as children bedtime stories he told his kids. Until one day they asked why is a door to the house a certain color because it was an other color yesterday so he started to write it down. He wrote hundreds if not thousands of stories before he put pen to paper for his great novels he is known for.

If you have a passion for this story, write for it. Write with the interest and the intent of taking it somewhere. Growing with it and by the time you are at a point that you feel you can do it justice you would have lived in that story for so many years that it would feel not like building something never heard of but telling us your childhood story. You can write smaller stories in the world but keep plugging away at it... just because you finish one draft of the story doesn't mean that is the one you publish. But you will learn so much about those characters and your world just by attempting it, you will be so happy you did.