Belt area soreness

I've been doing the exercise you taught us on Wednesday using the diaphragm to stretch forward, backward, left, right, and twisting. Let me tell you, I have been VERY sore around my belt line. Rolling over in bed is groan inducing. Lol! The sensation is interesting but I'll be glad when there's no pain associated with it. Is there anything in particular about this region that is important to pay attention to?