Thanks for asking the query,
After reading your history i suspect you have developed a periodontal abscess
in relation to an infected tooth, infection in the tooth has spread the the surrounding tissues leading to formation of abscess which is drained in the lump.
I would suggest you to visit the Dentist
get the checkup done take an x-ray of the tooth, drainage
of abscess is requires treatment will be either RCT or extraction of the tooth.
Take a complete course of antibiotics and analgesics.
Go for symptomatic treatment of complete mouth scaling and polishing.
Maintain a good oral hygiene
, use antiseptic mouthwash rinses twice daily.
Hope this helps out.