On the Linux system you can do following (Should be similar for other OS)
Check if mysql process is running:
sudo service mysql status
If runnning then stop the process: (Make sure you close all mysql tool)
sudo service mysql stop
If you have issue stopping then do following
Search for process: ps aux | grep mysqld
Kill the process: kill -9 process_id
Now start mysql in safe mode with skip grant
sudo mysqld_safe --skip-grant-tables &