The answer to this question can be found in the final paragraphs of the story. The first thing that happens is he rejoins his father, and then John prays and is purified. John's father is quite proud with his son, and John's father announces that John has now come back a man and a priest.
He touched my lips and my breast, he said, "You went away a boy. You come back a man and a priest."
Next, John announces to his father what he discovered. John tells his father that the "gods" that lived in the Place of the Gods were just regular men and women. John then tells his father about the entire trip. John wants to tell the rest of his people about his discovery, but his father warns him against it. His father tells him that knowing the truth might be dangerous for a people so used to believing something else entirely. John decides that his father is correct.
"Truth is a hard deer to hunt. If you eat too much truth at once, you may die of the truth. It was not idly that our fathers forbade the Dead Places." He was right—it is better the truth should come little by little.
In the final paragraph of the story, John tells readers that he does plan on eventually telling his people, so that they may return to the dead places to look for metal and knowledge.
Nevertheless, we make a beginning. it is not for the metal alone we go to the Dead Places now—there are the books and the writings. They are hard to learn.