Hello!
Start conservative treatment.
Ask him to follow proper ergonomics in his daily living. Proper postures should be learnt and followed strictly and always ask him to use proper chairs and bed to sit and sleep.
Ask him to start exercises to increase the strength of his back muscles. He has to have a proper body weight and a normal BMI.
He can take pain killers and he can also use hot and cold compress to get relief from his symptoms.
He can also take steroid shots for relief and explore surgical options if symptoms continue and if conservative treatment fails.
Take care!
Yes, that's definitely a sign that can be associated with a herniated disk. However leg pains are generally radiculopathy from the LUMBAR spine.
C5-C6, if radiculopathy present, would be the biceps and hands.
It is possible for the legs to be effected, but most likely from position compensation, or muscle tension compensation.
1 more thing: Is the leg pain and tingling on the side he sits on his wallet?