Most nodules in the lungs below 5 mm are benign nodules. They are often caused by previous lung inflammation or tuberculosis infection. No special treatment is required. Dynamic observation is enough. Check the lungs once a year. CT, if it does not increase, don’t worry about it. If it is larger than 5 mm, it needs to be differentiated from lung infection, tuberculosis, and lung tumors. It is recommended to check a blood routine and tuberculin test. If tuberculosis is ruled out, anti-infective treatment should be given first. If the nodule does not grow or shrink, consider inflammation. If the nodule enlarges, a pathological biopsy is required to rule out lung cancer.