A hard lump under the skin of the penis without pain may be caused by penile lymphangitis, penile sclerosis, condyloma acuminatum, penile cancer and other diseases. 1. Penile lymphangitis: penile lymphangitis, which is a small earthworm-like curved swelling under the skin of the penile coronal groove, usually does not cause pain. 2. Penile sclerosis: penile sclerosis is a benign progressive disease, mostly seen in middle-aged and elderly men. The main manifestation is the appearance of touching hard knots on the penis, which may or may not be accompanied by pain. 3. Condyloma acuminatum: Condyloma acuminatum is a sexually transmitted disease, caused by human papilloma virus infection, which can lead to the appearance of superfluous organisms around the external genitalia and anus, usually without pain. 4. Penile cancer: penile cancer is a malignant tumor of penis, the cause of which has not been fully clarified, mainly manifested as penile skin changes, with a single small and hard lump appearing on the skin. Patients with painless hard lumps on the penis are recommended to go to dermatology and dermatologic venereology department of hospitals for consultation, so as to clarify the cause first, and then go for treatment.