This post discusses how Nifty Options settlement is done.
First thing you must know is that in India Nifty options are cash-settled. These are European-style settlements. A cash-settled option is a type of option for which actual physical delivery of the underlying asset or security is not required. The settlement results in a cash payment + brokerage and taxes, instead of settling in stocks, bonds, commodities or any other asset. In India, options are allowed for trading before expiration (American style). Which means a trader can buy/sell an option and finish the trade before expiry ant time he/she wants. However, in European style cash settlement, the option contract owner is required to hold until expiration.