Thanks for asking the query,
Swollen lump at the back of the tooth that had developed suddenly can be due to allergic reactions, trauma to the region or bacterial and viral infections. Sore throat
occurs due to viral infections.
I would suggest you to visit the Dentist
and get the check up done, if necessary take the x-rays
Go for symptomatic treatment of complete mouth scaling and polishing.
Take a course of antibiotics and analgesic
Apply Dologel oral ointment topically over the affected area.
Maintain a good oral hygiene
, take lukewarm saline and antiseptic mouthwash rinses.
Hope this helps out.