Depending on the amount of discharge, this could be totally normal for a male dog. If it's just a small "drip" on occasion it's probably just what I've always called "love drops". Something you'll have to learn to live with.... If it's more than just a drop here and there, then a trip to the vet is probably in order.
If it's the "normal" love drops, most males are pretty good about cleaning themselves so a drop here or there is about all you see, however I have come across males that have owners that have a thing about their dogs cleaning themselves, and correct the dog for licking...in those cases, the drops can seem to be excessive.
Hope this helps.
Pam