Welcome to heathcare Magic!
If he did not have a fall as a result of shock
then the chest pain
is nothing to worry.
It is a pulled muscle due to shock which would resolve in two three days.
He can take OTC Ultracet
6hourly to ease the pain.
If he had a fall then he must consult a physician and should get Chest Xray, ECG,CBC,RFT.
To detect any serious lung/heart condition as a result of electrocution.
Wish you a great health!