Thanks for writing your query.
Viral fevers are usually associated with myalgia
i.e. pain in muscles.
This occurs due to some biochemical changes in the muscles as a result of fever.
It takes few days for full recovery.
Give your child proper rest.
Maintain adequate hydration of your child by giving him healthy drinks including pure water.
Hot fomentation and application of pain relieving gel will give him some relief.
If the pain persists, you give him pain killer like Ibuprofen
after discussing with his Paeditrician.
Give him fresh fruits and vegetables to increase his immunity.
I hope this is helpful to you.