hello thanks for consulting at hcm..
YOU have a broken filling in probably the right upper molar,,the boil on the gum might have resulted from periapical or
periodontal abscess,,
even though you have taken the medicine pencillin,, it was only to control the inflammatory process,
you need specific treatment for that abscess, by means of
incision and drainage,,and since one portion of the tooth is intact may be you can go for
root canal treatment followed by crown placement,,
Also you extraction of that small remnant of the tooth piece,,
So you need to take iopa radiograph to check for the progress of
alveolar bone loss, and extension of infection till what level,,
Kindly consult a oral physician or endodontist specialist asap for a check up and treatment,,hope it helps,,tc