The PCI rules for password management require that admin users change their password every 90 days.
So, after 90 days has elapsed, the next time you log in to your Admin it will ask you to change your password. Simply follow the prompts to select a new password. Per PCI rules, you cannot re-use the last 4 passwords.
If you don't want to change it "now", you will not be allowed to complete login. But your current password will let you get back to the change-your-password screen again.
NOTE: The term "password expired" is sometimes misunderstood by non-techie people who never used a mainframe computer decades ago. In this context it does NOT mean the old password has been deleted. It simply means you must now change it before you can complete login.