I think it's rice. And I think he's got either a porcupine or some dog's favorite rug lodged in his forehead.
there was rice and grenade fragments in his buttox ... doctor's took out rice, may have left grenade fragments. Of course, since Kerry refuses to release the documents about this incident, it's an open question. Regardless, either fragment or rice, the wound was errantly self-inflicted and did not qualify for the medal he received.