Hello and welcome to HCM, Swelling below jaw could be due to salivary gland swelling, lymph node enlargement or some soft tissue swelling. The region below the jaw contains lymph node, salivary glad and soft tissue structures. Lymph node can enlarge due to infections, inflammation or neoplasm. Similarly salivary gland can enlarge due to infection, inflammation or neoplasm etc. An aspiration cytology of thes welling is required to know the nature of thes welling. In aspiration cytology, the cells are aspirated from the swelling, spread on a glass slide and stained with appropriate stains. The stained cells are studied and the nature of the lesion is determined. Further management can be planned after knowing the nature of the lesion. A history of sinus infection increases the possibility of infectious lesion below the jaw. I suggest you to consult your primary healthcare provider for clinical assessment, investigations and thus management. Thanks and take care Dr Shailja Puri