The former Disney stars, both 23, dated briefly in 2008 and Selena insisted they were too young for a real relationship but have remained close friends.
She told Capital FM: "We were babies! We actually caught up the other day, and it's really fun to be able to do that. That, to me, was like puppy love. It was very sweet. He's lovely. I do have a love for him for sure."
Selena previously revealed that she loves bumping into former Disney stars such as Nick and his brothers as their experience as child stars was like going through high school together.
She said: "We grew up together! You know, it's so nice to be able to see people and talk about life. It's great to be able to reflect on your life. It's like high school in a way. I love them, they're the greatest, honestly."
Selena briefly dated DJ Zedd after her on/off relationship with Justin Bieber ended but is currently single.
Meanwhile, Nick, who split from beauty queen Olivia Culpo in June, recently admitted he is still "adjusting" to single life.
When asked how it feels to be single, he said: "Interesting. It's still an adjustment, getting use to my life on my own is an interesting thing.
"I'm in a good place of being young and grow and do what I need to do right now."