Boot into your System using Advanced Startup Options and select Command Prompt with Networking
By Default there is an Administrator account Hidden and without password and accessed over safe mode. If you aren't able to login through that, reset its password using following steps.
After logging in Open Command Prompt with Admin privileges (if it doesn't work, try opening it normally).
Type net user and press Enter Then you'll see the list of accounts.
There must be an account named Administrator/Admin
If yes, Type: net user Admin * or net user Administrator * (based on your user account available) and press Enter
Type in the new password for Admin/Administrator Account.
Now reboot and boot your system in safe mode and login with Administrator.
After successful login, Goto User Accounts Management, and change your account type from guest to Administrator.
Reboot normally and login to your account.