Thanks for writing to us.
Since the growth has developed below the dental work,abscess
may be developed at the periapical area of filled tooth,due to spread of infection into pulp and periapical area.
Please do visit a dentist
and get root canal treatment
or pulp capping done depending on the involvement of infection.
Take complete course of antibiotics prescribed by your dentist.
The growth will disappear once the entire pus within the growth has drained out.
Also make sure that you are maintaining oral hygiene