You don't say if the account is a Live:ID (MS Account) or a local user account.
If = MS, then you might try resetting it on-line using another computer or mobile device.
If = Local account, the you or either going to have to use third party software or you can try enabling the hidden Admin account.
I posted a method here
https://www.windows10forums.com/threads/keeps-saying-incorrect-password.1185/#post-12550
There are links to the installation media as well as a link to a step by step guide to the registry edit.
Read the my post and then read the guide that I linked to.