Pain shortly after the operation is to be expected. But when that pain persists weeks to months later, then the problem can become chronic. Some patients also report a patch of numbness over the area.
In a small number of cases, the donor site doesn't heal. Infection and wound breakdown can occur. Painful symptoms can result in a change in the way the person walks. In the worst cases, the pelvic bone fractures or the sacroiliac joint becomes unstable.
Most of these problems are really rare. Expect some short-term local pain over the donor site. If you notice anything unusual, report your concerns to the surgeon right away.