Hi,
Welcome to the ehealthforum. I am really glad to help you out. The few important causes of the lump on the jaw which need to be looked into are swelling due to enlargement of the one of the salivary glands. This can occur due to an acute infection in the gland and can be associated with a stone in the duct of the gland causing the swelling. However, it is a painful condition.
Another possibility is a sebaceous cyst. In this, the sebum (oily secretion) from the sebaceous glands can get trapped and result in the formation of a cyst. This is usually painless and may require surgical removal, if it causes any discomfort or is unsightly.
A biopsy of the swelling maybe required as it can also result from a swollen lymph node. It is very difficult to diagnose online without doing a physical examination. Hence, Iâll suggest you to consult a physician for the same. I sincerely hope it helps. Take care.