What is the ruling on swearing a false oath upon the Qur’an in court at the age of 13 for the purpose of warding off affliction and evil?

If an oath is taken falsely to avoid injustice, then there is no sin upon the swearer, because lying is permissible in such a case. Otherwise, lying in a "Ghamus oath" (a false oath taken intentionally) is among the grave sins. If this oath was uttered by a mukallaf (a legally responsible individual), then sincere repentance is incumbent upon him, and perhaps an expiation for the oath will also be required. However, if he was not mukallaf at the time of swearing the oath, then there is no sin upon him.