Try long with SL at 504 with Target up to 520 level.
Try lower time frame chart for better entry near 509-510
Try pullbacks.. refer https://in.tradingview.com/chart/BANKNIFTY/82XerBoY-Are-Pullbacks-Bad-Well-may-be-not-in-a-bull-market/
Never feel shy of accepting when you are proved wrong.
Dun risk more than 1-2% of your capital in a single trade.
On Lower timeframe.