Purchased a land which is challenged how can I defend myself

Actually I have bought arround 3 acre aggriculture land in my village .Land owner is my uncle .After arround 25 days of registration of land Uncle's daughter made case against myself .In which she shown when my father was mad and unconscious at that time this registration happen.But real matter is that my uncle has only two married daughter since 20 years.My uncle hates his daughter because she is not doing look after and want to take whole property. My uncle is mntally and phy fit but age is arrnd 80 yrs so that i am worry .Uncle wants result in our favour as much early .Reg dte is jun15