The 98 Degrees star and his wife Vanessa Lachey welcomed Camden John in September, and the singer revealed that his brother had advised him to make the most of the first few weeks.
"My brother said smell the baby a lot," he told Parade. "That smell of your newborn baby doesn't last very long but it's something you'll always remember.
"So I find myself sniffing his head and his neck. There is that baby smell that is so special, especially when it's your own baby!"
Nick also revealed that he has been motivated musically by his son, saying: "I'm actually working on a lullaby project that's inspired by Camden. I'm in the studio now finishing it up, so it should be out the beginning of next year."
He added: "It's some originals I'm writing and some classic ones, so it's a mixture."
Nick recently revealed that he named Camden after the street which was home to his wife's obstetrician's office.
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