A hard lump inside the gums may be a secondary infection of the apical cyst of the tooth, a gingival fistula, or a gingival tumor. The cause of the disease should be identified in a timely manner. 1. Dental apical cyst secondary infection: dental apical cyst secondary infection, cysts, cysts continue to grow will rupture on its own, such as timely anti-inflammatory and anti-infection, will be subject to repeated stimulation of inflammatory cells, resulting in gum tissue with a hard pimple, hard pimple is smaller, generally painless, such as pimple continues to grow, there will be pain, and accompanied by abscesses. 2. Gingival fistula: a hard lump on the gums may be a lump corresponding to the root tip of the gums, this lump is usually a gingival fistula, due to periapical periapical inflammation break through the alveolar bone, forming a fistula-like tissue. 3. Gingivoma: Gingivoma is usually caused by irritation, such as eating hard foods or nuts regularly, which may lead to hard bumps on the gum tissue due to irritation. There may be other reasons for a hard lump growing inside the gums, so you should consult your doctor to clarify the specific cause and treat accordingly if necessary.