When option expires without exercise...

#1
Hi!

Can someone help me in understanding what happens when option expires out of money. is there any action needed from option writer?

Let's say I have written a Put option for September Nifty at strike price of 4500. I pocketed the premium and broker kept the margin on the same.

Now, when it expires on 27th Sep, what am I supposed to do? Will the margin be returned back to me automatically on expiry?

Thanks in advance.