How to remove broken plug from socket

[purescentedflower]

the socket that I had my lamp plug into (in the garage) would not come out so I pulled harder (I know silly me)but the plug snapped and broke off sparks flew and burn the cord off but the cap of the plug is still in the socket. I have something else plug into the same socket and it feels a little warm. What should I do to get the piece of a plug out of the socket?

[Kit@HT]

Before you do any electrical work, turn off the appropriate circuit breakers so you don't injure yourself.