I had a tummy tuck years ago and I just had discharge come out my belly button. It is very stinky. I have never had this happen and am quite freaked out. The thing is I wouldn't think anything was wrong except small amount of goo got all over shirt. How concerned should I be? It is reddened in there.
Hard to say what’s going on without examining you. I would definitely seek medical attention from a plastic surgeon for an in person examination to determine the next steps.
My best guess is the navel is narrowing, so a lot of sebum is kept in, along with death cells. If you don’t rinse the inner part, the moist is what does this disgusting goo as well as the reddened skin. Please check with your attending for options