Francisco "Paquirri" Rivera Ordonez suffered the injury while fighting the bull in the town of Huesca and was in intensive care.
The bull's horn sank some 25 centimetres (10 inches) into Paquirri's groin but did not threaten any vital organs, doctors said.
Television footage showed the bull hoisting Paquirri into the air for a few seconds on a horn.
The bullfighter's nickname, Paquirri, is "Little Frank."
His father, of the same name, was gored to death, in Andalusia in 1984.
On Sunday, a Spanish man died after being gored in the neck while using his cell phone to film a bull run through the streets of Villaseca de la Sagra, central Spain.