How to recover loan from deceased borrower’s denying son?

We provided a loan of 11 lakhs to a prosperous businessman residing in Bangalore, with evidence such as bank statements, interest payment receipts, and acknowledgment messages. Unfortunately, the businessman passed away, and his son inherited his property and assets. The son has been consistently paying interest at a rate of 15% for the past two years. However, we find ourselves in urgent need of the money since last year. Despite making us three false promises to repay and resorting us to threats of harassment charges, the son refuses to return the money. We urgently require our hard-earned money, while the son is living a lavish lifestyle in a house worth 2.5-3 crore, owning multiple cars, and possessing other valuable assets. He is okay for us to pursue legal actions to recover the amount owed. He is even denying that the money was given to his father and not him. How best to legally go around this?