Change the config file/s for your apps to reflect a different user. Then grant privileges to that user to that db only in your mysql commands, with a unique password for that user. Reflect these in your config file and you should regain access.
[root@jensen-server ~]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1367 to server version: 4.1.20
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql> grant all on yourdb.* to yourdb_user@localhost identified by 'kHEv+UrJx4chpzhc88uApbU10InhdL0s9ujcvbd9VqIBgkRPfclLfHINjrN3fQhB67k1zkeQ';
then
mysql> flush privileges;
Query OK, 0 rows affected (0.07 sec)
mysql> \q
Craig