Duplicate entry in MySQL slave
First, let me start with a warning. Be very careful when you start messing with the data on the slave. It can really ruin the integrity of the replication setup.

That being said, if you are absolutely certain you don't want the slave to execute that particular statement, you can issue the following commands on the slave:

STOP SLAVE;
SET GLOBAL sql_slave_skip_counter=1;
START SLAVE;


This will skip the next statement in the replication log and move on. Here's the documentation for reference.