You need to reset the password for this. First start the mysql server instance or daemon with the --skip-grant-tables option. (security setting)
Then Execute these statements.
$ mysql -u root mysql
mysql> UPDATE user SET Password=PASSWORD('your_new_password') where USER='root';
mysql> FLUSH PRIVILEGES;
Finally, restart the instance/daemon without the --skip-grant-tables option.
You should be able to connect with your new password.
$ mysql -u root -p
Enter password: your_new_password
Hope this will help. You can get a better understanding from the AWS Training in Bangalore.