As long as it's a small amount of cheese, you can salvage the situation (having learned your lesson not to toast sandwiches in the toaster). Make sure the room is well-ventilated and you don't do this directly under a smoke detector: turn the toaster on for a couple of seconds at a time so the cheese that's stuck burns a bit, waiting until it stops smoking and then repeating so that it never catches fire or starts smoking out of control, until eventually the toaster can run without smoking.