If the module is exactly in submandibular region, it most likely points to an oral or oropharyngeal infection, however, if it is a bit more lateral and posterior, then it becomes the jugulo-digastric group of lymph nodes which indicate nasal or nasopharyngeal infection. As for a malignant lymph node, it has to be hard, stony fixed and absolutely painless. It the texture of node is painless but spongy, more probably it could be a lymphoma but a large, slightly tender mobile node is usually inflammatory! So in this case pain is actually good news!