I'm guessing it's the result of your circumcision. It's hard to tell on an infant how much skin the penis will actually need by the time the boy reaches adulthood, and if they underestimated or made any errors during the circumcision, you end up with little holes or tunnels.
I'm going to assume that the "paste" is because it's probably hard to clean properly in those areas. You might want to see a specialist about this for a second opinion.