There are two common causes of hardness in the neck: 1. Swollen lymph nodes in the neck, usually caused by upper respiratory tract infections, such as acute pharyngitis or acute bronchitis, can cause localized swelling of lymph nodes in the neck. In addition, it may be a malignant tumor of the thyroid gland or nasopharynx, which may cause swollen lymph nodes through lymphatic metastasis.2. Swelling of the thyroid gland, such as thyroid nodules, thyroid adenoma or even thyroid cancer, may cause a hard neck. If it is a thyroid swelling, it will usually be accompanied by swallowing activity. If it is a thyroid or lymph node, it can be diagnosed 80%-90% of the time with a local ultrasound.