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The gruesome new tat is down the middle of the front of the American rapper's neck, and looks like a bleeding slit in the skin.
He then shared a video on his story, with the text: "Here it is. It's my birthday week, love y'all."
Speculation has started about a possible link with a previous post of his, in which he revealed that he wears a drop of his girlfriend Megan Fox's blood on a pendant around his neck.
On Valentine's Day, the artist - real name Colson Baker - shared a photo of himself alongside Fox.
He wrote: "I wear your blood around my neck."
For her part, Fox shared a photo collage of Kelly, with the caption: "There goes my heart/ manifest outside of my body/ draped in the towering silhouette of a most unusually handsome boy.
"Magical and haunted/ kinetic and tortured/ ethereal and dangerous/ cosmic lawless eternal creative genius/ the journey will likely be perilous/ but there is no destination without him.
"Happy valentine's day rehab barbie."
How sweet, I think.
Oddly enough, Kelly and Fox aren't the first celebrity couple who have been known to wear blood around their necks as a token of their love.
Famously, Billy Bob Thornton and Angelina Jolie used to wear necklaces with a droplet of blood contained within them as they walked down the red carpet.
The latest addition joins his already extensive selection of designs.
He has what he referred to in a GQ YouTube video as 'a couple of three-in-the-morning tattoos', one of which is a text tattoo on his forearm which reads 'f**k off'.
Another was done in a 'really gross hotel', and is a Salvador Dali inspired design, which is on his back.
One of his favourites is a red double-decker bus, which he got when he was hit by a bus in Manchester, back in 2013.
Writing on Instagram at the time, he said: "I got hit by a ducking double-decker bus this morning within the first hour of me being in the UK.
"My head did this to the front of the wind shield.
"They x-rayed and released me from the hospital with no brain contusions/internal bleeding, just a bloody hip. I forgot they drive on opposite sides of the street here.
"What a f**kin' idiot. I'm getting a shot of whiskey and taking my dumbass to bed. Sorry if I had anyone worried."
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