mint 20.1 password recovery?

[Dave Stevens]

Somehow I've accidentally changed my user password on my Mint 20.1
install. I wrote it down and have checked repeatedly, I'm satisfied
that I'm typing it correctly. When I set up the system I used an option
to boot to desktop without a password prompt when the system is
repowered after an outage. I suppose that this means the effective
password is stored somewhere. Can anyone suggest where? or how to
proceed?

Thanks,

Dave