What happened to Jeroboam's hand when he stretched it out against the man of God?

Answer: It withered

Jeroboam's outstretched hand withered so he could not pull it back; it was restored when the man of God prayed.

“Now when King Jeroboam, who was at the altar in Bethel, heard the word that the man of God had cried out against it, he stretched out his hand and said, “Seize him!” But the hand he stretched out toward him withered, so that he could not pull it back.”— 1 Kings 13:4 (BSB)