I'm guessing you're probably rounding your back. Are you doing full squats? Also go to the doctor and get it checked, if everythings alright, when you squat again you need to pay attention to keeping your low back arched at all times.
Talked to my spotter... he said i was definitely arching my back. I think maybe I didn't warm up enough. It bothered me all night last night, but seems okay today. I guess I'll find out on my my next leg day.
I have hurt my tailbone snowboarding and I could feel the pain from it on squats for months....are you sure you didn't hurt it doing something else and you only notice it on squats?