Nifty is moving in a channel on hourly chart and seems like contraction which can take it either side. Upside after 21140 the sky is open but on downside there are many supports like 21840-21800 and followed by 21740 are strong support numbers. 21730 is monthly expiry since last 2 months and hence not easy to break.
Till the time Nifty is in this tight range OTM option buyers will loose money, though with time the support line is pushing nifty upward.