How can I tell if my foot/toe is broken?

Last night in a half-asleep daze, my foot twitched, and unfortunately hit the top part of my guitar with all the tuning pegs. The place I hit it is the spot on the side of your foot, just below the big toe where that bone sticks out a bit. Now, the area has a huge goose egg on it, as well as minor bruising. It also hurts on the bones from that point going up the top of my foot. It hurts when I'm just sitting there, especially when I touch it, and walking is also very painful. How can I tell if it's broken?