Registered Power of Attorney issued for sale of house

My father along with our family have living in a house which was on my Grandmother's name since last 25 years and the whole house is occupied by us. Recently I came to know that my uncle through my grand mother's Registered power of attorney issued to him to sell the house had sold off the house 13 years ago in 2005 which is still occupied by us and the owner legally has not claimed the house till now but retorting to illegal means. Further After seeing the copy of registered PoA issued to my uncle by my grandmother to sell the house on her behalf, the house number mentioned in the PoA document states 413 everywhere whereas the actual house number is 113 and not 413. The property is in Punjab but PoA registered in assam where my grandmother was visiting a relative that time supoosedly. The house when sold by my uncle was sold way below the circle rates. My grandmother is no.more. During the transfer and new registration of the house to the new owner, My father had been shown as a Licensee in the new registration deed or registry while transferring the house to the new owner. Also in the registry it is shown that we occupying 70% of the house but actually I am occupying the whole house. Is any legal way out to challenge the selling of house based on the above facts. Any help will be highly appreciated.