Please back up all data before proceeding.
Check the Internet Accounts or Mail, Contacts & Calendar preference pane to make sure you're not synchronizing Notes in more than one account.
If you're not, disable Notes synchronization temporarily. The notes will remain on the server and on your other devices, if any.
Quit Notes, if it's running.
Triple-click anywhere in the line below on this page to select it:
~/Library/Containers/com.apple.Notes
Copy the whole line of text to the Clipboard by pressing the key combination command-C.
In the Finder, select
Go ▹ Go to Folder
from the menu bar. Paste into the box that opens by pressing command-V, then press return. A Finder window should open with a folder selected. If it does, move the selected folder—not just its contents—to the Desktop.
The folder you're moving is named "com.apple.Notes" It is not the subfolder named "Data" or anything else.
Caution: If you move some or all of the contents of the selected folder, but leave the folder itself in place, the application may not launch. Moving the whole folder will cause it to be rebuilt automatically.
If you're running OS X 10.11 ("El Capitan") or later, repeat with this line:
~/Library/Group Containers/group.com.apple.notes
Re-enable Notes synchronization.
Relaunch Notes and test. If it works now, delete the folders you moved. Otherwise, quit again, and put each folder back where it was, overwriting the one that may have been created in its place.