My Dog Cries When You Move His Tail And He Doesn't Wag It Anymore. Why?

It may be dislocated.  My dog dislocated his tail and had the same symptoms but screamed when I touched it.
I took him to the vet and he popped it back into place... Problem solved.

However my Pugs tail does not curl up anymore and just hangs down.  I am very concerned and wondered if anyone else had this problem with their pugs tail.