It appears that you stopped Chantix
suddenly. In some people, sudden stoppage of Chantix has been shown to be associated with withdrawal symptoms
like irritability. But I am not aware of any reports of unilateral severe head ache and vomiting
after stopping Chantix. So, in my opinion, the best option would be to consult your doctor and rule out other causes of head ache and vomiting. like migraine
, head injury
etc. If you still feel that the symptoms are due to Chantix withdrawal and are not improving with time, you can restart Chantix and gradually taper it off under supervision of your doctor.
Hope this has been of help. Best wishes.