Third part interest

Purchased through sale deed property in feb 2007 without knowing that the seller had won the case in jan 2007 against one other claimant of the property. I dint even know that there was a case. In june 2007 without any party informing the court that the property has been sold, the appeal was filled by other claimant in high court and the seller to me was diected not to creat third party interest till the appeal is heard also the seller could apply for any variations as and when they arise. Its been ten years now i am constructing the property and the other claimant has applied for stay against me. The court still doesnt know that before giving the order in june 2007 property was already sold and therefore the stay was invalid. I am in the possession of the property since last ten years have electric meter house tax three families living in the property. The seller who sold the property to me was also in possession past ten years before me. What shall be the best course and possible outcomes