Have you checked to see if your keyboard region has maybe reset? I can see that causing issues if the password has special charicters like #, ", @ or £.
Failing that, look up UBCD, it has a tool called Offline NT password & registry editor. Give that a try. I've not used it since at least win7 so idk if it still works for 10, but i'm guessing it'll work (hopefully)
Also keep UBCD, super useful.
afterthought edit:
This will only work for local accounts, just incase someone comes along later on