What does yours look like, what is it made of? Please post a picture of yours so we can offer you some good ideas.
Here are some from Pinterest:
here is some ideas for you
you can also use it just as a decorative piece on a shelf or table if you don't have a pen to go in you could buy a cheaper pen to put in the bottle or near it
It would look pretty sitting on a shelf just the way it is, or you could add a flower with the stem cut short.
Hello, why not use it to store pens, pencils letter openers, etc.
You can check out these great and cool ideas from pinterest https://www.pinterest.com.mx/jdsjd65/ink-wells/
Hello two ideas I can think of is ……possibly a business card holder or place to put a small potted plant maybe a miniature sedum
How big is it? You could use it as a bud vase.
Use it as a little vase for flowers
You could consider selling it on eBay!
Hard to say, since there are so many styles, but all the suggestions above are sound. Also you could sell it. Etsy has tons for sale for comparison.