It smells 😢

Eve

So yesterday I changed baby’s diaper everything was fine. Nothing was smelly. But this morning I breastfed her and going to change her diaper and she was smelling bad, I thought she pooped while I was sleeping and didn’t notice. Wtv. I changed her and saw her ombilical cord turned and almost off. I smelled it and it was bad. The upper part is dry but under it looks wet. I know it should be wet but it is. What should I do?