Is it free moving, as though you could almost pick up the lump if it were not held down by skin? If so, it might just be a benign fatty tumor, a lipoma. If it is a lymph gland that is up, that is more concerning. If it were a salivary gland, I would think you would see some signs such as gingerly eating or you might smell very bad breath. Obviously, I am just going by experience and not sure where the lump is. If you are that worried, go by your gut on this. If it is getting larger overnight, a vet visit could be warranted sooner rather than later. I would want an abscess seen before the infection goes systemic. Let us know.