My cousin sold our joint-owned property without telling me, what can I do?

I am deeply troubled. I co-own a piece of land in Nagpur with my cousin. Recently, I found out he sold the entire plot to someone else without my consent or any discussion. I was not in India for the past year and had no idea about this transaction. I trusted him to manage it while I was away. I feel betrayed and confused about how to get my rightful share or reverse this sale. What legal steps can I take to challenge this sale?