Hi,
NSE only provides the LTP(last traded price).The lot size is available in the fo section of NSE website where u see market today link.Its a dropdown box where u can select Nifty and Nifty stocks to see their details of puts and calls of current month and next month(S) if available.
Your brokerage site can provide the current bid/offer details of the contract.
Be sure to read FAQ's on options and risks involved as well as brokerage on options.
Hope this helps.
Regards
Amit.