Mysterious lump opinion

Question
Hi,
I just got back from taking my dog to the vet. (I know that you are not a vet, I just want the opinion of another long-time dog owner)  My rottweiler, Nico, has developed a large mysterious lump on his right side on the rib cage.  It's similar to if you cut a baseball in half and stuck it on his ribs.  It doesnt feel fluid-y, its relatively firm and seems to hurt him a little.  He is also extremely lethargic but still has a good appetite.

Our vet doesn't want to do an x-ray or biopsy and thinks that it is a bruise (by thinks, I mean that he touched it for about 30 seconds and told me it's a bruise).  However he hasnt had any kind of injury recently, especially to create a large lump in just a few days!  He mentioned that he could have broken ribs, but then said an x-ray wouldn't show anything.  Then he asked me if I kicked my dog, (NO), and told me I was just overreacting.  For the time being we are following his advice to give Nico an anti-inflammatory and wait a week.

Am I crazy?  Have you ever experienced a dog having a large protruding "bruise" for no apparent reason?  Outsider's opinion:  Am I overreacting?

Answer
I was going to refuse your question because this really is a medical issue, but thought better of it.

Anytime... **ANYTIME**... one has doubts over something he was told by his vet, it is time to go and get a second opinion. I have never inquired about a lump on any of my dogs and not have the vet aspirate it, or at least attempt to. And it does seem to me that if your dog DOES have broken ribs that would show up in an X-ray.

Over-reacting? No, not reacting fast enough. Get your dog into a different vet!