Simply change or reset your MySQL root password by doing the following:
Stop the MySQL server
sudo service mysql stop
Start mysqld
sudo mysqld --skip-grant-tables &
Login to MySQL as root
mysql -u root mysql
Change MYSECRET with your new root password
UPDATE user SET Password=PASSWORD('MYSECRET') WHERE User='root'; FLUSH PRIVILEGES; exit;
Kill mysqld
sudo pkill mysqld
Start mysql
sudo service mysql start
Login to phpmyadmin as root with your new password