Hi.. Thanks for the query.. If you have an abscessed tooth then it will cause severe pain even after taking painkillers until the pus will be drained off and infection will be resolved.. Even if the tooth that is abscessed is in upper jaw then it can also aggravate your sinus infection due to close proximity of roots of upper teeth to the floor of maxillary sinus. If you are not able to see a dentist right now, atleast consult an Emergency room and get evaluated. They can advise you a prescription of antibiotics like amoxicillin and clavulanate like Amoxiclav or Augmentin and along with it stronger painkillers like Ketorolac for relieving pain.. An injection of painkiller can also be given for faster relief from severe pain.. Once you can reach your dentist, you should get an x ray of the tooth done. If tooth is still in a condition to be saved you will be advised to get a Root canal treatment done but if there is gross decay then extraction is advisable.. Hope you get well soon.. Regards.