I forgot my password but can access the phone via fingerprint

Your iPhone will eventually require you to enter your passcode. TouchID and FaceID are not meant to be permanent replacements for your passcode.

If your iPhone is asking you for your passcode to unlock it, you need to either enter it, or erase it and restore from a backup using the procedure linked at the top of this page.

RIGHT NOW: Back up your phone to iCloud (not to your computer; it would require your passcode) so you can restore your phone after it becomes disabled when you fail to enter your passcode correctly several times or after any of the other reasons a passcode would be required. Then to save yourself having an access problem when you need the phone to work intentionally restore the phone and the backup→Restore your iOS device from a backup - Apple Support

Eventually your iPhone will force you to enter your password. Touch ID and Face ID do not replace your passcode. If you are unable to successfully enter your passcode when your iPhone requires it, the device will become locked and possibly erase itself.

See Face ID, Touch ID, passcodes, and passwords - Apple Support

Particularly this point under When a device passcode or password is required

• The user hasn’t used their passcode or password to unlock their device for 156 hours (six and a half days), and the user hasn’t used a biometric to unlock their device in 4 hours.

This means you can unlock your iPhone via TouchID. Isn't that interesting?