Given your description, I'm guessing you snapped a wheel bolt when trying to undo it? If so, support the car on an axle stand, get the wheel off and see where the bolt has snapped off. I would also remove the brake caliper (make sure you support it out of the way, don't leave it hanging on the hose) and you should then be able to remove the brake disk after taking out the little disk retaining screws (small cross heads that hold the disk onto the hub). If there is a stub of the wheel bolt sticking out of the hub you could soak it in plus gas, clamp some mole grips onto it, lean on those with a foot and then tap the hub around the area with the stuck bolt and on the end of the stuck bolt. This should shock load the bolt and once it lets go the pressure on the mole grips should keep it turning. Heat and then rapid cooling can also help.
If you can't see a bolt stub you will have to get it carefully drilled out.