Did you ever figure out what caused it? I just noticed mine has a ring around it today too and all the way inside. Though the color is a definite dark pink, not a light pink, and goes all the way into the belly button. I’ve lost 70 lbs now, but I’m nervous as to what it could be? It doesn’t itch or hurt, and I’m not sure how long it’s been like this bc I have to kind of lift my skin to see the inside of my bellybutton but I noticed it when I got out of the shower today. I hope it’s not an infection!!