What happens if selling position is not closed on expiry day?

The question is pretty basic. Let's say I have an sold an otm call option with Rs.20 as premium (lot price 1500). If on the expiry day I forgot to close the position or could not close the position due to less volume, and the option price becomes zero what would happen to my capital (let's say 1L) Now: I neither have the capital or the discipline to do F&O. I am just curious about this.