I have a hard, somewhat painful lump.

Hi,

Welcome to the ehealthforum and I am really glad to help you out. Your concern is regarding the lump under your jaw. The most common cause of such lump under the jaw is swollen lymph node. Lymph nodes are small (1-2cm) and bean-shaped nodes. They are very important to your body keeping you healthy. Lymphadenopathy (swollen lymph nodes) is usually caused by a viral or bacterial infection. Other causes include allergic reactions, arthritis, cancer, metabolic diseases, and an overactive thyroid (hyperthyroidism). Since you are having a history of cigarette smoking, so definitely this needs to be evaluated.

The second possibility for this lump is of a boil or an infected cyst.

The third possibility is of a salivary gland swelling. Any infection, stone or tumor of the salivary gland (submandibular gland) can cause a lump under the jaw. My sincere advice is to consult a physician and get it evaluated. CT scan of the area and fine needle aspiration cytology and biopsy will help in confirming the diagnosis.

It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care.