What breed of dog is he?How big is the lump?Is it on the shaft of the penis, or the abdomen around it?Is he neutered?
Thanks for answering my questions.
The lump is something that could have many causes: inflamed lymph node, sebaceous cyst, lipoma. Because of her age and the description you gave me of what it feels like, I'm suspecting it's a lipoma or a sebaceous cyst, but I'm just guessing.
Here's more reading on lipomas and other cancers: http://www.thepetcenter.com/exa/lumps.html
On cysts: http://www.petplace.com/dogs/sebaceous-cysts-in-dogs/page1.aspx
On lymph nodes: http://www.peteducation.com/article.cfm?cls=2&cat=1614&articleid=319
The only way to positively identify what sort of lump or bump your dog has is, unfortunately, also through a trip to the vet. A fine needle biopsy (where the vet inserts a needle into one of the bumps and tries to aspirate/pull out material to look at under the microscope) will tell the vet, without question, what sort of problem your dog is having.
I hope this helps.
I think he would be fine waiting until Monday.
It's doubtful that it's a hernia...those don't just appear as a general rule.
It sounds to me like a lipoma. It's in a fatty part of the dog and he is older, so that's my best guess.