Cough is a protective reflex of the body to expel out the mucus or any irritant factor from the respiratory tract which is most of the time assosiated with cold due to any viral or bacterial infection . A proper examination is required to find the cause . As a home remedy you can start with steam inhalation . Cough can be treated with cough suppressant or antitussives as per the cause. For cold antihistamines are useful and nasal saline drops are also benifecial .

Please consult Pediatrician physically