hello there,
According to your history i can suspect your
root canal treated tooth may have some remnant infection which was left un explored .
This infected tooth has gone worse and you have developed a
periodontal abscess due to spread of infection to the underlying tissues.
The lump or swelling you can notice is nothing but the abscess cavity and it drains the pus in the oral cavity .
This type of periodontal abscess needs to be drained and compressed in position and then followed by a course of antibiotic and
analgesic will subside the symptoms of pain and swelling.
once the abscess is drained the infected tooth can be retreated by root canal procedure to devitalise it permanently and save the tooth or of the prognosis is poor the tooth can be extracted.
get an x ray done the affected area and approach a
dentist for the treatment.
meantime you can start with antibiotic
augmentin 625mg with analgesics two times daily, this helps in subsiding the swelling and pain.
i hope this helps,
take care.