hi there ,
According to your history i can suspect some remnant of the tooth like root piece or infected tissue has left in the alveolar bone that 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 which may drain 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 root piece can be extracted .
you need to get an x ray
done the affected area to confirm the presence of infection, approach a dentist
for the treatment.
i hope this helps,