On a closer inspection of the charts, I find that there are actually two shoulders on each side and two necklines. First one which is drawn by joining bottoms of 30th September and 18th October was at 6003 and it was broken decisively yesterday. The volumes had been falling from left shoulder to the right shoulder. This is a typical characteristic of H&S formation. Note the huge volume on breakout yesterday, though this is not necessary for H&S top. (Market can go down because there is no buyer at high price).
The distance measured from top of the head (6284 on 14th Oct) to the bottom of head (5985 18th Oct) is 299 points. Break out was at 6003. I therefore expect nifty to fall up to 5704 which is minimum implication of H&S formation.
The 50 DMA is currently placed at 5834. Therefore a pullback from 5870-6000 to the neckline is possible.
Since the H&S formation is not visible in weekly charts, I do not expect it to have a severe impact lasting more than a month or two.
These are my observations. I welcome criticism if I have erred on technical details.