This is a terrible complication. This is called central necrosis, which means that all the skin in the area that you see has died. You need an experienced surgeon to take care of this. This is not an easy situation. It will take months just to get the infection under control, and the skin to cover the defect. He’ll need a lot of work to be able to look normal again.
This is caused by the placement of too many wounds (grafts) in the area, using an instrument that made wounds that were too large, and causing a loss of the blood supply in the area of the scalp that is very sensitive to blood supply interruption. Many patients came to me over the years with this type of complication from inexperienced surgeons. It takes a great deal of wound care by an experience team to treat this kind of problem. Hopefully, you can afford a good surgeon or plastic surgeon with the experience to manage this situation.