I've done something to my ankle?

I was skipping/power walking (i know bad idea) across my class room today to get a dictionary. Halfway across the room i miss stepped and the side of my foot was on the ground and all my weight went onto it at a right angle. I herd a small crack (like you hear when you crack your knuckles) and then suddenly felt severe pain. I quickly sat on the closest table and it felt really painful. After a few minutes of sitting there i started to feel like i was going to vomit and i felt all the colour from my face drain. I hobbled over to sick bay and my shoe started to feel tight. I took my shoe off and sat in sick bay for 20 minutes with ice on it. During the 20 minutes it started to feel worse especially with the ice on it. My dad came and picked me up after about half an hour of being in the sick bay and my foot hurt a lot more to put weight on then than it did when i went to the sick bay. Its now about 1 1/2 hours later since i got home and its a little swollen and there seems to be this blue sore swollen lump on the left hand side of my foot (its my left foot). I got up about half an hour ago to go to the bathroom and the pain of walking on it is getting unbearable, i had to roll myself around my house on a desk chair it was so bad. Im keeping it elevated on a pillow. What else should i do? What do you think it is?