Hi,I would make an appt.with a good doctor and get checked.It could be many things,and I would not jump and worry yourself that you have cancer.They are so many things that can cause the problem you are having.We all tend to lean toward the worst.I have known 2 or 3 men with a problem like you are speaking and it turn out to be something that was treated very easy,with a doctors help.Good luck.
You need to be seen by a doctor, no one here can give an accurate diagnosis and the possibiluty of there being a problem further indicates the need for a immediate medical evaluation. It may be nothing, but only a doc will be able to tell.
Good luck,
Andi