If India wanted to enforce the sanctions they would. I'm sorry but what America found out is they can't just enforce sanctions across the globe in the way they thought they could.
The only point of the sanctions is to make Russia sell their oil for less, to lower their profits. Yeah, India buys their oil, but Russia doesn’t have that many other buyers anymore, and it’s a lot less convenient for India to buy Russian oil, so India can really pressure Russia on the price of their oil.