A pimple on the side of the genitals may be caused by condyloma acuminatum, syphilis, penile cancer and other reasons. 1. Condyloma acuminatum: it is a sexually transmitted disease, mainly manifested as scattered or clustered proliferation of small pink or white papillary bumps on the penile skin or glans, soft, when the foci increase in size and fusion can be corns or cauliflower-like, the typical can be diagnosed by the naked eye, and atypical can be diagnosed through biopsy and pathology examination. 2. Syphilis infection: for people infected with genital syphilis, when the disease develops to the chancre, it will also be manifested as lumps on the genitals, which are usually red in color, and will form ulcerated surfaces when it breaks down, which can be clearly diagnosed by combining with the medical history, clinical manifestations and laboratory tests. 3. Penile cancer: it can also cause pimples on the genitals, early manifestation is wart-like erythema or pimple-like, with the progress of the disease, it will touch the hard lump in the prepuce, and there can be bloody or purulent secretion, which can be diagnosed by combining with clinical manifestation, ultrasonography and physical examination. There may be other reasons for a lump on the side of the genitals, and it is recommended to consult a doctor in time and treat it actively.