Is smelling cigarette smoke without smoking it forbidden? And what should I do about that?

Merely smelling cigarette smoke unintentionally, without intending to inhale it, carries no sin, as one is not held accountable for that which is unintended, and because it is difficult to avoid. Sitting with a smoker is not permissible except out of necessity or for a recognized legitimate benefit, while enjoining them to good with the best of words.