When to see your doctor right away:when you develop priapism. An erection that lasts 4 hours or longer. This painful condition can lead to long-term penile damage.
When you loose erection suddenly after hearing a pop sound during overextension of erected penis as it may indicate penile fracture. Condition best managed within first 24 h.
If you experienced any trauma to penis or develop a boil in the penis (especially diabetic men or men with poor immune system). Infections in the penis spread very quickly and if not treated may result in catastrophic lose of tissue.