How do I stop my ceiling fan from wobbling?

A fan came with my room in the apartment that I am subleasing and the light went out. During the process of trying to unscrew the dome cover to access the light, I think I over-rotated the entire motor or something when I was trying to figure out exactly how to get the thing undone. Its some cheap Harbor Breeze fan that couldn't have cost more then $30 dollars so maybe the quality was shot? Anyway, after I finally replaced the bulb and re-secured the dome, the fan rotates pretty violently on a high setting and even sways freely whenever I pull the cords to turn on the light and/or fan. What did I do and how can I fix it?!?!?!