You likely damaged other stuff on the board sensitive to having reverse polarity applied. It will take some time and expense to replace the obviously bad component(s) only to see that the board still doesn't work.
That is too bad because if you had applied the reverse polarity to the external power connector instead of directly to the shield Vin pin you would have suffered no damage because the arduino folks installed a reverse polarity protection diode between the connector and the Vin trace just for such newbie type of mistake.