Because nicotine isn't the only things in cigs, our bodies go through a lot of changes when we quit. If you read through the quit smoking symptoms thread people mention body aches, sore throat, etc. Cigarettes had a calming effect and it could be stress related. Maybe you're tensing your back in some way. Some people complain about heart burn and back pain when they quit.
Hope you feel better and it goes away soon.
Hope you feel better and it goes away soon.