L.M.
I don't know exactly where in your side the pain occurred, but it has happened to me for various reasons.
1. Dehydration. Were your lips also cracked? I find I have to drink water before bed and keep water next to the bed while I am pregnant.
2. Ovarian cyst. I had one of these with both pregnancies, and it's not a bad thing. My doc told me it helps produce extra progesterone to support the pregnancy and usually resolves itself in the second trimester.
3. Positioning and/or gas. OK, to be honest, I am a much gassier person while pregnant, and the positions I sleep in can aggravate the issue. Try walking it out, perhaps, and see what passes.
It is unlikely threatening to your pregnancy, but my doc has always told me that my peace of mind is as important as any medicine or procedure they can offer while I am pregnant, so if you're really worried, see if they can squeeze you in.
Best wishes.