Hello,,, your friend need to be examined, to know what's the actual problem is,, and we need to know whether the defect is birth (bony) or due to some swellings in the skin or soft tissue of scalp. If the swelling is from soft tissue if scalp. Then no need to worry, it can be treated medically or surgically. So don't worry, convince your friend to see a doctor and consult a general physician.(or general surgeon).