There can be many reasons for this hard lump. It can be some bony growth or it epulise or it can be due to some infected tooth. For this you have to go to dentist who will do clinical examination and take xrays and find out the cause of this hard lump and do the treatment accordingly. If it is some bony growth or epulise then it has to be excised but if it is due to some infected tooth then infected tooth will be either root canal treated or it will be pulled out by dentist.
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