Thank you for your query.
You may be right.Exertion and sleeping on the couch can produce back pain
due to poor posture.
Kindly apply a painkiller gel to the local area and give him some regular paracetamol
tabs for a few days.
If the complain persists then consult a specialist.
If you have any further queries you are free to consult me.
Hope this answers your query.
Wishing your child a speedy recovery.
Have a nice day.