How to challenge a fraudulent mutation (Inteqal) of land?

You must file a Suit for Declaration and Cancellation of Document in the Civil Court. Under Section 42 of the Specific Relief Act, a civil court is the proper forum to determine title and declare forged deeds void. Revenue authorities (Tehsildar) cannot decide complex questions of title or fraud; they only maintain records.

Also file an application for temporary injunction (Stay Order) under Order 39 Rules 1 & 2 CPC along with your lawsuit to prevent your uncle from selling or transferring the land while the case is pending.