Brief Answer:
It could be musculoskeletal pain
Detailed Answer:
Hi
As per your description,it looks like Musculoskeletal pain.Tablet containing Thiocolchicoside will help.
If there is no response, Ultrasound abdomen has to be done.Right sided Kidney stone/Ureteric stone has to be excluded.
Nothing to worry
Hope I answered your query.If you have any questions,I will clarify further.
Wish him good health
Regards