What to Do to Reduce or Relieve the Muscle and Joint Pain Caused by Accutane?

I am on roaccutane for 4 month now. It was ok so far a part from the usual side effects, however after increasing the dose to 40mg a day, I developed joint and muscular pain specially on the beck of my neck (it is like a constant stiff neck),I can not move normally. Is there any painkiller I could possibly take in order to help to end up the pain? I am loking forward to hearing from you. Thank You!