Welcome in H.C.M.
I have gone through your query about your nasal obstruction
and pain in nose on pinching it along white spot inside nostril. Your past history of dental abscess
and sinus problem .
As you asked relationship between dental abscess and sinusitis
, in this connection I would like to say that pre molars and molars of upper jaw may develop sinus infection
because they are attached to alveolar border of maxillary sinus.
Regarding your present problem I am suspecting as you are having sinusitis and that may be confirmed by doing X-Ray of paranasal sinuses
if found so than that should be treated by an E.N.T. specialist.
Hope your query is explained.