Thyroid cysts sometimes hurt and sometimes do not. A thyroid cyst refers to a round, fluid-containing cystic structure found in the thyroid, generally 2-5 centimeters in diameter, smooth, usually painless or with mild pain, and can move up and down with swallowing. If the cyst is large or there is bleeding inside the cyst, it may cause some compressive symptoms such as pain, difficulty swallowing, breathing difficulties, and hoarseness. Therefore, whether a thyroid cyst is painful generally depends on the size of the cyst and whether there is bleeding inside it.