If it's stll on Windows 8.1 I can't be sure this will work but if you have Windows 10, you can hold down the power button for ten seconds to turn the laptop off. Do that a few times and it will get fed up and offer you StartUp Repair options, one of which will lead you to a Command form.
Try typing
net user Administrator /active:yes
and hit the Enter key. If the command is successful, type exit to get out of the form and restart.
With some luck you'll get an extra login option - the system Administrator account. If that lets you in, it will also let create a new User Account and delete the existing one.
Once you've restarted once more and logged in to the mew account, the syntax to shut down the Admin account is the same...