Running nose is most often caused by viral infection....it is self limited disease.
So the treatment includes only supportive management..
As u have said nly cold...allegra syp(fexofenadine 30mg/5ml) 2.5ml daily twice would be sufficient
Next Steps
if cold is associated with cough and fever do consult a local paediatrician
Health Tips
sudden weather change or travelling could also cause this running nose...so avoid those by providing warmth to child like using sweaters headcap etc