HELLO AND WELCOME,
the lump may be due to many reasons.
your filled may be decayed and involved periapical area also.
get an x-ray of the tooth to rule out any underlying pathoses.if there is periapical infection and abscess
,then remove the filling.extirpate entire infected pulp.abscess can be drained and curetted.
obturation of canal should be done only after removing vital pulp completely.
deep scaling has to be done to remove gingivitis
complete course of antibiotics should be taken.
novacaine injection can also cause hard lump if there was abscess already.
this is due to occurence of antibioma.
crown has to be placed only when the hard lump subsides.