On expiry of a weekly contract, exchange will introduce next weekly contract on rolling basis. The contracts will expire on Thursday of every week. In case the Thursday is a trading holiday, the previous trading day will be the expiry or last trading day said NSE.
An expiration date in derivatives is the last day that a derivative, such as options or future is valid. Future traders can also “roll” their position. This is a closing of their current trade, and an immediate reinstitution of the trade in a contract that is further out from expiry.