is there anyway to disable password and enable fingerprint to unlock ultra power save??

[Leannea]

Good morning All, I am hoping someone can help me. I stupidly turned on ultra power save whilst in the country for holidays without access to power. ..problem is i don't know what the password is as I only set it up when I originally purchased the phone...I use the fingerprint option instead. I've now been without my phone for a week and a half. ..does anyone know how to disable the password and enable the fingerprint scanner whilst in ups? Have pulled out battery SIM charged it fully...no joy. Your help would be greatly appreciated .

Or, do I need to take it back to the reseller to fix??