Neighbour not allowing to construct boundary wall

Hello sir, 

Firstly you are required to understand your rights which means whether you have the proper right over the property and approved, valid documents of the same. If you have this then even grampanchayat cannot stop you from constructing a wall unless it is illegal and violates zones or property of someone else. 

If you have recieved a notice, then you should send a reply of that notice to grampanchayat attaching the valid ownership documents and property documents along with boundary details. 

If grampanchayat physically stops you from constructing then go to a higher court and request a court order to allow construction. As per order 39 rule 1 and 2 of cpc, you can ask the court for temporary injunction to stop blockage or prevention of construction.

Along with this if neighbour tries to block or stop you from doing construction then you should file an FIR. 

Keep records of all the incidents which you can present in court as an evidence such as photographs, documents, etc.