Regarding Injuction orders in joint property

I had retired from my service during Feb, 2018. I have started construction work of my house on my share of land which has been allotted to us through a family partition on [deleted] which has been reduced in to writing but has not been registered. All the co-sharer are having possession of their respective share and enjoying their share ever since i.e. 1975 including me as per the family partition. Other co-sharer have constructed their houses on their share long back. The entire land is joint land as per the revenue record. One of the co-sharer sold his share of land along with old house during 1914 in a specific khasra no. which is far away from my share of land to a third party without the knowledge of other co-sharer and in violation of the conditions of the family partition. The purchaser has now filed a civil suit against me seeking stay of construction on the plea that his land is less. Kindly advise me: - what is legal solution available with me -Whether purchaser is entitled to take injunction on other co-sharer -What is the sancity of family partition