Incorrect Password after changing 'user'

Hello all. Newbie here and not very tech savvy. I was working on my laptop just fine this morning and when using a specific program noticed it was saving work as a previous user. So I went to accounts and changed the user name to mine. Now when I start the computer and am prompted for password it just says "incorrect password" even though it still shows the "password hint" as the same as it used to be and the user pic is still the old one.

I am freaking out as I have deadlines due today and can't access my computer!
Please help! THANK YOU!

**Edit to add that I was signing-in with a local acct, not an MS acct.

Brink said:

Hello ETW, and welcome to Ten Forums. :)

If you used netplwiz to have Windows automatically sign in to your account at startup, then you'll just need to set up netplwiz again to update it with your new user name with password again.

Sign in User Account Automatically at Windows 10 Startup

I did not or at least I don't think so as I never heard of netplwiz. Any other options to access? I really appreciate your help. I am going nuts.

Thanks.

Understood. But don't I need to be already signed-in to do that? As for how this all started, I was using a program (Bluebeam) and when saving my work noticed it was saving using the previous user as "author". So I went to accounts and changed the one and only existing user name to mine. Did not change password as I was not prompted to do so. Upon restarting the laptop, as normal my picture came up, even my password hint was the same, but using the same pw as always got me the "incorrect password" note over and over.

**edit: when I say previous user, this particular laptop was used by one other person previously before it was handed down to me. He was the original user when it came out of the box.