Hardness in the chin after hyaluronic acid injection is commonly caused by hematoma and localized aggregation of hyaluronic acid. Hematoma usually disappears in about 1-2 weeks, and localized aggregation of hyaluronic acid may take 1-3 months or even longer. 1. In the process of hyaluronic acid injection in the chin area, it may damage the capillaries and form hematoma in the deep tissues, which will disappear on its own in about 1-2 weeks generally, and no special treatment is needed; 48 hours after the injection, you can accelerate the absorption of the hematoma by applying hot compresses. 2. Part of the case is due to improper injection of hyaluronic acid, uneven distribution of hard knots, usually takes 1-3 months or even longer to relieve; if the hard knots affect the appearance, it is recommended that the patient go to the regular medical institutions for lysis of enzyme injection treatment. 3. Other: we can’t rule out the formation of local chronic granuloma due to the foreign body rejection reaction of the injected filler; if accompanied by redness, swelling, heat and pain at the same time, we can’t rule out the local infection. In summary, the chin part of the injection of hyaluronic acid produces a lot of hard knots, it is recommended that the patient to the regular medical institutions, clear cause of the disease and timely symptomatic treatment, in order to avoid adverse consequences.