My son has been coughing on and off for the past...

What is the treatment 
Common cold is one of the most common viral infection that infect the upper respiratory tract to cause cough and other symptomes and Cough could be treated using Chlorpheniramin 4 mg| 5ml syrup with a dose of 2,5 ml twice daily, in addition for the blocked nose you can use Oxymetazolin nasal spray twice daily for 3 days or simply washing the nose with normal saline or water, Consult a pediatrician for follow up.
Investigations 
After proper physical exam, cbc should be done to look for infeciton ,Chest XR  to look for chest infectio.
Causes 
Common Cold 
Pharyngitis 
Chest infectio
Our advice 
Consult a pediatrician for follow up.