By his calculation, Jonathan Valena, a tattoo artist who goes by the name JonBoy, has given more than 20,000 permanent souvenirs. The one that changed his life was inked on June 16, 2015. On that day, Mr. Valena placed a white dot on a woman’s middle finger. It took him about a second.

“It was that little white dot that blew things up,” Mr. Valena, 36, said recently. “The phone started ringing off the hook. Talk about God’s grace.”

Mr. Valena once thought he had to choose between his love for tattoos and his love of God. But in this case, his good fortune may have more to do with another all-powerful force in the universe: the Kardashian-Jenner family. The finger that Mr. Valena tattooed belonged to Kendall Jenner, a model and younger sister of Kim Kardashian.

One Instagram post later, he found himself hailed as the latest cool tattooer, a Dr. Woo of the East Coast, a Sailor Jerry for the young Hollywood and fashion crowd.