Hello and thanks for consulting HCM. Without seeing the lump to learn its exact location, color, x-ray films, only general observation can be listed. This means your case may be completely different from some other case of pink hard mass. With that being said, many lumps--hard or soft--are often signs of infection. The tooth may be infected with cavity bacteria, or rotting of dead nerve if the tooth has been dead. the hard mass can be: an abscess a cystan epulis a granuloma an irritation (denture) hyperplasia a mucocoele a haemangioma to know the exact diagnosis proper clinical examination and a biopsy or FNAC (if needed) can be done.i would advice you to visit a dentist. Hope this ans helps. Take care Regards Dr. Shesh