;D

You got a flat, and we all get them sometimes. Most likely the tire was under inflated, and you had a pinch flat, where the tube was pinched between the rim and the ground. You'll need a new tube (about $4, and some tire levers ($5) I'll link you to an article about how to fix a flat-

http://www.sheldonbrown.com/flats.html

Just search "how to replace a bike tube" in google or something, ask a friend, or go to a local co-op/shop.