...
After a user has created a Sticky Note for a matter, the Sticky Note will continue to appear until someone deletes it. If a user simply closes a Sticky Note, the Sticky Note will re-appear the next time a user navigates to that matter.
...
Instructions
To close a Sticky Note.
Click the 'X' in the upper right of the Sticky Note window.
To delete a Sticky Note permanently.
Click ‘Delete’ at the top of the Sticky Note window
...
Related articles
Attaching a Sticky Note to a Contact, Attaching a Sticky Note to a Matter