Brief Answer: See primary care physician, Detailed Answer: Hi and thanks for the query, The fact that the lump appeared so fast and is tender or painful, makes the possibility of an acute infectious process or inflammatory process most probable. It is very likely that this should be an enlarged lymph node. it would be necessary to know if you have had any infection, wound, tooth , mouth or throat infection lately. This could be an enlargement of the lymph node which is a normal regional immunological response. Other rare causes of neck lumps like cysts and lipomas should also be considered. An infected cyst can be painful. But the scenario here makes it not very likely. A lipoma is unlikely because it is not generally accompanied by any pain. I suggest you consult your primary care doctor first for a complete clinical review. Simple Analgesics for the beginning like ice parks and Acetaminophen could be sufficient to control the pain as you wait to see your doctor. Feel free asking follow up questions in case you got any specific concerns. I would be glad contributing to your well being. Kind regards as I wish you good health. Dr Rogers

---