Thanks for asking the query,
Lump at the roof of the mouth can be due to abscess arissing from the broken tooth.
I would suggest you to visit Dentist
and get the clinical evaluation done, take an x-ray of the tooth.
of abscess is required, Get the root canal treatment
completed for the tooth.
Go for complete mouth scaling and polishing and curettage.
Take complete course of antibiotics and analgesics.
Maintain a good oral hygiene
, take lukewarm saline and antiseptic mouthwash gargles twice daily.
Hope this helps out.