What Causes a Hard Lump on the Forehead?

Hard lumps on the forehead are most often attributed to osteomas, or hard, bony growths in the skull, according to plastic surgeon Dr. Amil Shah. Osteomas are not very common, but are usually benign, slow-growing and asymptomatic. Osteomas may be hereditary or formed at birth, according to the National Library of Medicine. While only symptomatic osteomas require treatment, many people who do not have symptoms still choose treatment due to their unsightly nature.