Sharing a photo of herself with a reddish mark on her upper lip, Charli wrote: "Not a sexy pout and no filter can cover it!"
"'What started as just a very small red dot on my lip, turns out was a pre skin cancer that really needs to be removed!"
"While pregnant I can't [have it surgically removed]," Charli continued, "but we're trying a strong laser which hopefully will do the trick."
Charli then urged all her fans to get a skin cancer check.
"I've always had pale skin but all skin types need a skin cancer check! [It] only takes a few minutes no matter your age. It's worth it!"
Charli went on to thank dermatologist Dr Michael Freeman at The Skin Centre clinic on the Gold Coast, but clarified her Instagram post was not sponsored.
Charli and partner Liam Talbot are expecting their first child together early next year.