hello and welcome,
this can be due to the infection in your affected tooth has spread along the sinus tract,which results in pus discharge into nasal and paranasal air sinuses
visit your dentist
and get an x-ray of that area to rule out the cause.
emergency access opening of the tooth should be done in such cases.
take cap.spamox-500mg,thrice daily for 3 days,and
tab.divon-100mg,twice daily for 3 days,must be taken to subside the accumulation of pathogenic micro-organisms.
if any abscess
seen periapicaly,it has to be drained out and curetted by gracey curettes.
the permanent filling should be given only after the canal dries up completely.