Inheritance of willed property

Hello! Experts,

My Aunt died in 2002 and left behind an unregistered will. My Aunt never married and had no children. In her will she left her home in Jabalpur, MP to 3 people - me, my sister and a family friend (Mrs M). Mrs M used the will to transfer the property solely on to her name. Mrs M and her family have been maintaining and residing in that home since 2003 without the permission of me or my sister. I have now received news that Mrs M is looking to sell the home. Question - How can I put a stop to the sale of this home and exert my rights as a heir? 

Thanks