At school (25yrs ago) I stood up when the teacher entered the class and my chair fell to the side. My friend who I sat next to was ill and someone had taken her chair away. I sat down onto the heating pipe which ran along the floor behind. Such agony!!
To cut along story short, my Mum took me to a chiropractor, who did intensive massage on the area, evey week for months. It killed!! However, it did get better and I was able to carry on as normal.
I do notice though, if I feel under the weather, then my coccyx aches and I tend to change position alot in my chair as sitting on it for too long it starts to ache.
Hope this helps.