OK, (re)boot your system and select 'single user mode'. When asked for the root password, enter it. You're now on the commandline. Don't be afraid, we'll help you out
Next, issue this command:
mv <old-name-of-dir> <new-name-of-dir>
Example: if you named it afzal and you want it named masood, issue this command:
The cd command changes the working directory to /home. Check if the dir is renamed properly with
You can ommit the /home suffix of that command if you're in the /home dir. When all is right, reboot your system with
Let it boot normally.