a number of answers; check out this one also; make sure that no instance of mysql is running, always brought by not ending your sessions well. get the super user rights with
sudo su
and type your password when prompted to (remember nothing appears when you type your password, so, don't worry just type it and press enter). Next go to your terminal and stop all mysql instances:
/etc/init.d/mysql stop
after that, go and restart the mysql services (or restart xampp as a whole). This solved my problem. All the best.