Issue of boundary wall attach with neighbour.

We have bought a plot and build it 13 years back. The backside boundary wall is common to our backside neighbour and us. Our contractor has build that wall on the place of original wall which is actually inside neighbours area. To our backside wall we have attach a bathroom, store and a gallery. In the bathroom and store we have 9 inches wall out of which 4.5 inch in our area and 4.5 inch in neighbour's area. Only in the gallery we have a 4.5 inch wall which is in neighbours area. For all the wall construction we didn't ask our neighbour any money. Now we are constructing our upper floor and this time as we know the issue, we are constructing all the wall in our area. Still he had issues. He has suddenly came up 2 days before roof construction and saying that you are using my wall in the ground floor, So i will bring a stay to your work. Is it legally possible. We assured him that we will make a wall inside the gallery too, still cause of jealousy he want to stop our work. He is trying all his ways to stop our work. Are there any loop holes which we are not aware and he can use to stop our construction. Can you help us with the basic legal laws regarding construction. And also how can we punish him legally, if he create any disturbance. Can we ask him for the money of the wall, we have constructed in his area.