I am no expert in hatched chickens but as a nurse, this is what it looks like to me. The long thing hanging looks like the remaining yolksac that was not absorbed. The loopy looking yellow thing coming out of his abdomen appears to be a loop of intestine. If the yolk didn't fully absorb, it's possible that the navel area is still open and the looks of intestines popped through. This is what I would do. Wash your hands well and VERY gently try to work that loop of intestine back into his abdomen. This will have to happen quickly...before it starts to close. If you are able to get it back in, take a wet piece of gauze or wet thin strip of cloth and wrap it around his little body to hold it in. If you are successful, the navel should close on it's own within a day or so. It's very susceptible to infection right now. Good luck!