Cancelation of agreement

Hello All I got my share from my in laws for my kids. I sell it to another buyer ( a builder) in 1.5Cr . Now I want to cancel the agreement nd return advance which is Rs 10 Lacks only for which buyer asked to make draft. He had not given us any agreement copy , he made us signed 2 agreement one in which full amount is mentioned nd another in which only 50 Lacks Mentioned. Now he is asking to low the price by 25 Lacks which I am not agreeying . My daughter is minor so Guardianship NOC is required for which my buyers lawyer applied on my behalf nd attached copy of agreement in which 50 Lack amount is mentioned. Nd also threatning us tha t if we see/ Visit our shop he will ask his goons to beat us. Also he is saying you can go in court as I am widow nd can't afford to go the legal process Now my question is Can I cancel my agreement, as it's not registered yet He is trying to force me indirectly but i dont have proof that he is saying all those things My only blunder was that i didn't took my lawyer with me nd can't tell my parental family too because of some unavoidable issues Please help nd guide me