That just looks like an unhealed navel. It'll close up. In the meantime, just keep the chick clean, and separated which you're already doing. Keep it separate so the other chicks don't peck it and make it worse. Putting ointment on it is good too. I use triple antibiotic ointment for rough navels.My chicks finished hatching in the incubator last night, so I moved them to the small brooder today. One has a really swollen navel, looks all red and mean there. I don't know what to do. I put neosporin on it and gave her a separate box as to not spread anything contagious. Any knowledge or suggestions? Thank you!