Once in while i get pain when chew in one of last teeth on upper right side.dr checkd says maybe sinus or cold related. is this possible? sounds odd.

Odd but true: The roots of the upper back teeth are often close to the floor of the sinus. When a patient has allergies, sinus infection, congestion, etc. They may experience what they perceive as 'tooth pain' when in reality it's related to the maxillary sinus. I have had some patients who question this relationship until they realize on their own that their toothaches coincide directly with their sinus infect.

Very Possible: Sinusitis can cause pain on the maxillary posterior teeth. Don't discount what your dentist is telling you... The advise may be right.