Hi and thanks for the query,
Looks like he is suffering from pharyngolaryngitis...ie .. infection of the throat and voice box.
If he has been suffering for many days then he will require an appropriate antibiotic.
Please visit a doctor for a prescription.
Other measures that will help him are..
1) Warm salt water gargling.
2) Complete voice rest.
3) No yelling or whispering.
4) Steam inhalation 4 times a day.
5) Plenty of fluids.
6) Avoid cold
foods and drinks, and air conditioning.
Regards, Dr KIshori.