Hello and welcome to the forum.
Interesting problem.
Which version / build of Windows 10 are you currently using (Home, Pro, Enterprise, 10586.318)?
Is this a work / domain joined computer?
Are there any other user names to select in the bottom left corner of the sign-in screen or an option to select "Other user"?
Have you tried the Ctrl + Alt + Delete keyboard combination to see if that produces an alternate screen?
Have you tried using the power option icon while holding the Shift Key on your keyboard to Get into the advanced troubleshooting option and using Startup Settings to launch Safe Mode / Safe Mode with networking?
What input device are you using (wired USB keyboard and mouse or wireless)?