If you want to check your username when you are logged in you can just type whoami
If you need to get username at your local machine, you have all users listed in /etc/passwd
.
You should have your account listed on greeting screen, if you didn't hide it after install.
However if you don't know your username nor password I think that there is no way to log into your account - if it would be so easy then it would make no sense creating accounts - even in windows they repair backdoors caused by recovery mode and cmd mode.