My thumb hurts so much! How do I reduce the pain? ?

You should have told the teacher. So what if he got mad. His attention should be your safety and well being even when you make a mistake. It would have kept the school liable for any trips to the dr. as well. You should tell him tomorrow. He may get really mad that you hadn't told him right away but he'll get over that as well. Sorry, no help for the thumb, just wanted to let you know it was a bigger mistake in not reporting the accident than the accident itself was.