Hi, An erection can become painful if the penis remains erect for long without becoming flaccid (priapism) or if the blood supply is not adequate (ischemia). Your condition requires medical intervention and you need to see a doctor. Second, painful erections can be caused by phimosis and preputial adhesions so if there is anything strange about his penis or testicles such as color or morphology you need to seek for help. The treatment of priapism to remove blood from the corporeal bodies. Sometimes medication in the form of an injection can be used to achieve this. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Ivan R. Rommstein, General Surgeon