Hi there,
I am sorry your boy was hurt. This may be a sprained tail.
Please compare your boys tail to these photos:
http://www.woodhavenlabs.com/coldtail.html SOURCE
I printed this for you:
Cold water tail," "limber tail syndrome," "broken tail," "dead tail," "broken wag" are all euphemisms for a relatively common occurrence in sporting dogs. The tail of the dog hangs down from the tail base or is held horizontal for three or four inches and then drops down. A flaccid tail episode appears to be a painful, but relatively benign affliction that can occur after swimming, after a heavy hunting day or even after a bath with cold water or water that is too warm. It is not always associated with swimming or water, but can happen after a heavy day of work that involves a lot of tail action. The majority of limp tail cases have been reported in sporting dogs or hounds -- Labrador Retrievers, Golden Retrievers, Setters, Pointers, Flatcoats, Foxhounds and Beagles are the breeds frequently named. Almost all dogs that suffer through an occurrence return to normal within a few days. Affected dogs may or may not have a repeat incidence during their lifetime. [It is this author's experience that symptoms will repeat in the same animal and can be trigged by something as simple as a cold water bath.] This affliction has been described by the layman as a "sprain," fibrosis or a "cold in the tail." The affected dog is miserable at the onset and the tail is painful. If neither the dog owner nor the veterinarian is familiar with this condition, it can be disturbing
Here is the rest of the link:
http://www.thelabradorclub.com/library/coldwatertail.html SOURCE
If he has "cold tail" it is safe to wait.
In the meantime apply warm compresses three times a day for five to ten minutes.
He can also have 5 mg or aspirin per lb with food every ten hours for two days.
Please let me know how he is doing.
Best wishes for him,
Teri
Healthcare Expert
Expert in canine health and behavior. 20 years of experience with dogs