The main causes of testicular nodules are the following: one is hard inflammatory nodules left after epididymal or testicular inflammation; secondly, testicular epididymal cysts can also manifest as hard nodules; in addition, testicular tumors can also appear as hard nodules. The specific situation needs to be clarified by taking into account the medical history, the absence of accompanying symptoms, and the relevant examination results. Testicular cysts, also known as sperm cysts, are formed gradually and usually have no uncomfortable symptoms, but a few patients may experience testicular swelling and pain. In addition, if previously suffered from orchitis or epididymitis, some patients will be left with a harder nodule called inflammatory nodule after the condition is controlled. Secondly, testicular tumor may also have a relatively small hard nodule in the early stage, but most of this condition will gradually increase in size. In either case, if a hard nodule is found, it is best to go to a hospital urology department for an ultrasound examination of the scrotum first. To sum up, the causes of hard testicular nodules are mainly cysts, inflammation and tumors, which need to be clearly diagnosed by combining medical history, physical examination and relevant auxiliary examinations.