Brief Answer:
Possibly due to viral cause

Detailed Answer:
Thanks for asking on HealthcareMagic.

I have gone carefully through the details and understand your concern. Most often such symptoms are due to viral infections and antibiotics are ineffective in such cases. Irrespective of treatment it usually spontaneously resolves in 5-7 days. Some children are more prone to catching cold and recurrent episodes are seen. Such infections are frequently associated with an allergic component and if cough or nasal discharge is present it is advisable to give some antiallergic like cetirizine once daily for next few days.

You need to give steam inhalation to your child. It helps in reducing the congestion. Just sit with your child on your lap and place the source of steam before you. The water vapor will be in the air and automatically the child will breathe it in. Water vapor will reach deep inside and would help in diluting the cough and thus would provide relief. Use Nasoclear Saline Nasal Drops in case of nose block.

Please be patient. It may take a few days for the recovery to occur. It should spontaneously resolve in 5-7 days.

Hopefully that would help. Feel free to write back in case of further queries.

Regards

---