Person disputing the land plot which is in our possession since 2009

My Odisha based father bought a land plot (1300 sqft, part of a larger plot measuring 9100 sqft) in Bhubaneswar in 2009 and the plot is in his possession (small boundary wall around the plot) since then. He had checked for Encumberance Certificate for 27 years prior (till 1982) and after finding that the land record (RoR) is in the name of the seller he purchased the plot. He got the mutation of the plot in his name in 2018 after winning a civil case against one of the relatives of the seller. SInce then, we are paying the government tax for this plot also. In December 2020, we started building a house on that plot, and the owner of the neighbouring plot came to stop the work, threatened the labourers, and claimed that he was the owner of all of the plot land and claimed that his grandfather had bought the whole 9100 sqft plot in 1965 from the father of the person who sold the plot to us (in latest ROR dated 1989 is in the name of the son who sold the land to us). To this respect he had filed a civil case in court in 2013 and in 2020 he won the case ex-parte and had got the mutation of the remaining 7800 sqft in his name in August 2020. He didn't object to this RoR of 7800 sqft but as soon as we started building, he came to oppose. Now he has got a status-quo from lower civil court. What is the legal option and opinions for us and how should we proceed?