The hard knot left after acne is usually caused by local blockage not completely discharged or fiber repair after inflammation, which can be eliminated by general treatment, topical medication, physical therapy, surgical treatment and other measures. 1. General treatment: keep the skin clean and hygienic, avoid squeezing and scratching the lesions, eat a light diet, eat more vegetables, quit smoking and alcohol, eat less too sweet, too spicy, too greasy, etc., stimulating food, ensure a good night’s sleep, life and diet are regular. Keep your bowel movement smooth. 2. Topical medication: Adapalene gel, tazarotene gel, benzoyl peroxide gel and so on can be used externally as prescribed by the doctor, the main purpose is to play an anti-inflammatory, dissolving keratin. 3. Physical therapy: infrared radiation can be taken to promote the dissipation of inflammation. 4. Surgical treatment: if the nodule does not subside, it can be removed directly by surgery if necessary, and attention should be paid to the wound care after the surgery. The hard nodules left after acne need to go to the regular hospital for examination and standardized treatment as prescribed by the doctor.