When you go to your meeting, DON'T show your temper. It might be hard, but be as pleasant as possible. Tell him/her exactly what happened and how you were unaware that you were breaking any rules.
When it comes to dorm life, getting along makes it much easier on everybody so try and work things out.
Also, I know what you mean by how bad dorms are. My senior year my dorm was no bigger than a closet (literally, I had to put thr dresser in the closet to save space). To top it off, the hot water heater broke so I was taking ice cold showers in winter for about 3 months until they managed to fix it.