I wouldn't worry too much unless it lasts for a couple of days. It can be a pinched nerve, or any number of other things. I would research smoking and autoimmune disease, you may find it thought-provoking. It this problem persists, please see a doctor. If you don't have a regular GP, an urgent care doctor can perform a routine neurological exam, and make referrals if necessary.
I hope you feel better. (Just a thought, do you have any pain in you middle back? You may just need a chiropractic adjustment.)
Tammy
you have reached an MS chat forum for patients. None of us are doctors.
did you mean to go to this site?
curious, why would you START smoking at 20?