Issuing Rs50 stamp paper and 2 blank checks against loan received from personal lender/friend

Dear sir, I had taken a total loan amount of 8L in staggered form from start of 2019 to end of the year. Since my amount was rising the lender demanded a signed Rs 100 stamp paper and 2 blank cheque. Since Rs100 stamp was not available at that time he demanded to pass on Rs 50 stamp paper 2nos to him which I couriered him. The amount I received was through bank cash deposit from other state. Since covid my situation became worst but some how I managed to get back and since 2021 I'm repaying the amount through bank transactions only. I have already re paid 6.5L through the bank but the account no he had given me belongs to some other persons current account. Rest balance 1.5 L would be paid within 7-10 days. But now the situation is such that he's demanding 25L total on the 8L he gave me. Total transactions are through bank , the lender had deposited cash at all time in my account and I have repaid him though in others account. The account no. was provided by the lender himself. I'm worried now what can he do with Rs50 stamp paper and 2 cheques issued. My first priority would be to settle the matter mutually by paying him additional 2-3L in interest... Need your suggestions....