A Boy and His Dog (1946)

11 year old Davy discovers that a chained gentle dog, Buck, is badly wounded around the neck because of the thick, tight collar he is made to constantly wear by his unfeeling owner. When Buck comes through the fence and becomes stuck, Davy removes the collar. Even though the boy tells him to stay in his owner's yard, the dog follows him home.

Unfortunately the movie A Boy and His Dog is not yet available on HBO Max.