Creating an original character is one thing, but writing a story for your OC is a different skill altogether. It’s only natural to want to see your OCs in action once you’ve designed them so if you want to write a story with your original character as the star, why not start by writing story fragments.
Remember to be kind to yourself about this. If you can’t come up with a story that flows yet, then… well, don’t. Chances are if you’re reading this then you’ve got some fragmented scenes in mind, so write those with no expectation that they’ll become anything else. Write one-scene wonders or flash-fiction, in other words. One of the nicest things about writing these is that they’re finished quickly because everything’s so self-contained. They don’t have to link to any other story and you don’t have to explain how the character got into, or out of, the scene you’re writing.
You might just find that once you’ve finished, you want to write how the story came about or what happened afterwards. Perhaps two of your fragments will seem to fit and you can write the bridge between them. You won’t know until you’ve written some. Try it!