I have a Black Male Cocker. His hind area is very tender to the touch, his tail is down. Can dogs break thier tail? Isn't made of cartliage?

Tails are made of bone -- similar to the vertebrae in the spine. Yes, they can break, just like any other bone. I did find this site that might help answer some questions.
Dalmation's experience
Dog Sore Tail
regards,
toodles

The tail being down doesn't necessarily signify that it's the tail which has been injured - if your Cocker is docked, then tail injuries are unlikely anyway. I would get your vet to check your dog out - hind end discomfort could be caused by any number of things such as infected anal glands or even a back injury.

Jane

Dogs do bruise their tails, they are quite painful and seem to hang limpish. They do get better by themselves but takes a few days. Maybe just check with your vet in case it is anything more serious.
Dawn.

Had a similar problem with a freinds staff a couple of weeks ago and it was a slipped disc

Exactly, Mr. Murphy. My oldest dog had a slipped disc 3 years ago. Operated on succesfully, and seemed OK, then last year his tail went completely floppy, although no sign of pain and discomfort. Now OK (after Reikki treatment, posted about previously). Also know a PBGV who suffered from a 'flooppy' tail, and some degree of discomfort - rest and aa heat lamp fixed it.
Gwen