Sell Agreement Expired

My father made a sell agreement with a party, which expired at the end of Feb. Until the last day other party was saying that he needs some time to arrange the money. But without any notice/information he has registered his presence at the registerer office saying, he is ready for the purchase but buyer is not available. Also he never sent us any kind of notice for registry during the agreement term. Now we do not want to sell our property as the agreement is expired and he was failed to made the payment. What should be our action now to avoid any problem in future.