You need to check the same when you executed the sale deed with that person. The title search made at that time was significant. Presently the possession is with you and the registered sale deed also. Till no one establishes any claim you don't have to worry. You cant create any new document. You need to rely on what you have. Try to sell it on the basis of registered sale deed and other documents in your custody. It is however not a very clear title in your hand.