Hello Naaz,

If you are having a backlogs in the under graduation you will not be eligible to persue post graduation even though you have cleared the TS PGCET. It is because you will not be given a pass certificate in UG as you have one backlog, Therefore you might not have a chance to get an seat in MJ. 

Hope this Helps.

Good Luck! will be happy to help with any other doubts.