I forgot the password for one note

From the article below.

To unlock a note, you need to enter the password that it's locked with. If you forgot the password, Apple can't help you regain access to your locked notes. You can create a new password, but this won’t give you access to your old notes. A new password will let you password protect any notes that you create going forward with the new password.

How to lock notes on your iPhone, iPad, and iPod touch - Apple Support

Onenote uses the same Office365 password you use with your Microsoft account. You’ll need to contact Microsoft support to reset your Office365 account password.