It's okay to have a world without ever writing a story set in it. Nobody is telling you that you have to do anything with your world; sometimes it's fun to just imagine. That's perfectly fine.
If you just want to be able to remember the world you are creating and not feel like it's going to waste, you could try just writing about it. Not a story, just writing about the world. Write about whatever comes to mind about it, as if it were real and you were writing nonfiction. Jot down/type up whatever details you can think of. If you prefer typing, you might create a folder so you can organize notes about different things in different files. If you prefer handwriting, maybe a physical folder. Or a binder, if you don't think a folder will fit it all.
Okay, so maybe you're adamant about writing a story. An actual story with a plot and everything.
A story is not about a world. A story is about characters in a world. Let's take, for example, a couple of stories with awesome worlds: Harry Potter and Star Wars. People love these worlds--a quick glance at SFF.SE will tell you that. But what people really care about--what makes them want to keep reading or watching--is the characters. We want to know what happens to them. We want to see how they overcome the challenges they face.
In Star Wars, there's spaceships, exotic planets, and the Force. Cool, right? But these merely serve as a setting in which to put some characters. We care about Luke and the other protagonists, and we want to see them succeed. The world provides a fun place for their story to occur: it provides its own challenges that contribute to the story.
Likewise, in Harry Potter, most people keep reading because they want to know what happens to Harry. That doesn't mean the world is unimportant; without the magical world, Harry would just be an orphan who grows up with his nasty aunt and uncle, then goes to college and lives a normal Muggle life. That wouldn't be a fun story.
So, you need to start with some characters. Try to imagine a person in your society. What kind of problems will the society give them? What might they do to overcome these problems? What other kinds of people are in this society, and how might they help or hurt the main character?
These questions will help you come up with some characters and some conflict--the beginnings of a story. Now, you just need to organize it and flesh it out into a cohesive plot.