i was using Face ID to unlock my notes, now it’s asking me for password and i never set any password before, how i can open it right now ?

If you want to lock more notes in the future, you still can. As the support article you came here from discusses.. you can reset that password by going to Settings > Notes > Password > Reset Password.

This will allow you to lock new notes using a new password. Any old notes that were locked with the previous password will still be locked until you figure out that password.

you did set up a password, because it's the only way you can enable Face ID to unlock them. Face ID itself is not a 'password', Face ID is a convenience, there is always a password behind it.. a password that you cannot forget or lose track of.

Similarly, if you forget your iPhone passcode and you are prompted for the passcode, you will not be able to access your phone

Face ID is NOT a replacement for passwords. You may also use Face ID to unlock your iPhone. However, it is simply impossible to set up Face ID without an iPhone passcode, so I hope you've made note of your passcode for the phone, for without that, there will be times you MUST enter your iPhone passcode and if you don't know it, you'll have to fully erase the phone.

The bottom line is you did create a password for your note, you just don't remember you did. And a note cannot be locked without creating a password. As mentioned above, you have unlimited numbers of guesses, but until you remember the password you created, the note will be locked and there is no way to bypass that.

The ONLY option you have is to recall the password. If you cannot recall the password, the note(s) will be locked forever. Apple cannot unlock it. We can't unlock it. ONLY you can unlock with the correct passcode.

This is why is vitally important to note passwords somewhere. As you are now learning, not having done so, means you may have notes you will never be able to unlock.

Something as simple as a little notebook, can work well for jotting down all your passwords. Then keeping that little notebook somewhere safe for future recall.

You'll need to use the password that you set for the note; you set one up when you locked the note.

you have unlimited guesses to unlock.