why does my penis ache when erect?

Answer 1

Please see a urologist. Many things can cause pain on erection. It would be best to see the doctor to find out the cause so it can be treated. The treatment also depends on the cause. Some causes are:
trauma
stds
being bitten (animal or human)
infection (many types and several locations)
priapism (constant erection) - if you have this you need to see the doctor now!
cancer
sickle cell anemia
injury (even over manipulation)

You doctor will ask you how long you've had the pain, when it started, if is comes and goes, does it hurt all over or in one location, etc. Of course, he will also examine you to see if he sees any reason for your discomfort. Good luck!