If you have already had your username and password then you just need to update capability and role into a database.
Go to wp_user table and locate your ID from there i.e. in my case its 2. And then go to wp_usermeta and look for meta_key = wp_capabilities and user_id - 2. Edit that row and change meta_value to
a:1:{s:13:"administrator";s:1:"1";}.
Again go for meta_key = wp_user_level and user_id = 2. Edit that row and change meta_value to 10. Don't change other rows where user_id is not your own.
Additional Notes:
The roles are saved in form of serialized PHP array. Change the user role you want to assign to the current user by changing the meta_value as:
Subscriber
a:1:{s:10:"subscriber";b:1;}
Contributor
a:1:{s:11:"contributor";b:1;}
Author
a:1:{s:6:"author";b:1;}
Editor
a:1:{s:6:"editor";b:1;}
Administrator
a:1:{s:13:"administrator";b:1;}
