thanks for sharing your concern.
don't worry.it is sure, you don't have any cancer, as you don't have any such symptoms. wishing you good health, now i will explain you what you actually have in your teeth.
you have gum problem , that is periodontal abscess
or it could be related to teeth that is periapical abscess
, that is why you have soreness.
if it is periodontal abscess it is because of poor oral hygiene
, deep pockets and infection to gum tissues.
if it is periapical abscess it could be due to a cavity (decay) of your upper molar , which has progressed and has led to periapical infection.
for this you must visit your dentist
and get an xray done.
on evaluation of your oral cavity (mouth) and xray exact diagnosis can be made.
after that you can start the treatment accordingly (either for gums or for teeth).
meanwhile use chlorhexidine
mouthwash 2% twice daily for a week this will reduce your oral infections.
also do warm saline rinses frequently to localize the infection.
for your pain you can take tab combiflam
5oo mg every six hourly for three days.
hope it helps.
for further query you can contact me through my profile.
take care thanx