Hi Magesh,
As per the documentation, “When there is no unique key on the table, there is no choice but to change the data on the slave, and pt-table-sync will detect that you’re trying to do so. It will complain and die unless you specify --no-check-slave”
http://www.percona.com/doc/percona-toolkit/2.1/pt-table-sync .html
Generally, its unsafe to make changes on slave directly but if you don’t have any other way, you have to use --no-check-slave option. Because by default, pt-table-sync will always give error when there is no unique index on table.
Have you tried to use that option? are you facing any issue with that?