The 23-year-old rapper may be inked from head to toe now, but he used to be ''so scared'' at the thought of going under the needle, and only seeing how much body art his pal had made him change his mind.
He explained: ''I was always so scared to get one and then I got one.
''We were working on [debut album] 'Stoney', and then we had a tattoo artist came through, and I was like, you know what? Justin Bieber's got some tatts, and I love you, but I know I'm way tougher than you.''
The 'Rockstar' hitmaker's first design was a Playboy bunny, but it didn't last very long as he had a run-in with Justin, 24, on the basketball court a few days later.
Speaking on the 'Tonight Show Starring Jimmy Fallon', he said: ''I guess Justin was watching this interview in the future when I said I was tougher than him 'cause we played basketball like two days later and he knocked the whole thing off.
''It was just blood dripping down my hand. It kind of looks like my tattoo got dropped in lava, but I like the story anyways.''
Justin previously admitted he loves the fact he's made his ''body a canvas'' with his many tattoos.
He shared some photos of his body art on Instagram and wrote: ''If tattooed didn't hurt everyone would have them. Well maybe not very one!! Over a hundred hours of hart work on my body and I wouldn't take back a single one.. I ABSOLUTELY LOVE ART AND IVE Made my body a canvas and it's SO MUCH FUN.(sic)''
His new album Underneath It All is out now.