6. Swollen neck
If your neck swells suddenly, go see a doctor immediately. If the front of your neck is swollen, it may be an indication of a thyroid problem. If you have a high fever and swollen lymph nodes, you have mononucleosis. A swollen neck may also be a sign of infected or cancerous lymph nodes. While some swellings are harmless or a sign of a minor infection, others can be a reason for concern.