Hello....
I can understang your concern....the post Herpes pain is really very severe.....
Homoeopathy definitely has good medicines which can help him....
But will need more info as to which side/ location of the rash, the type of pain, also more details like his Nature, Temperamental changes due to pain, etc....
So please consult a Good Homoeopath nearby....
Health Tips
Give him things which are cool by nature like...Gulkand, Buttermilk, Dhaniya powder.
Also you can apply some juice extracted from Coriander leaves on the affected area.