Hello, running nose and sneezing is a common complaint in kids of this age group and mostly it is viral in cause. This viral common colds take its own time to recover. Advent is a antibiotic and to be used only if there is suspicion of an bacterial cause as it wont work against a virus. Viral illnesses just need symptomatic treatment. Cheston may work.
Next Steps
Consult a doctor to find out whether the etiology is viral or bacterial[Mostly it should be viral]. Never self medicate the child. If the above medications were started after consulting a doctor then its fair enough.
Health Tips
First of all , dont be tensed as long as your is active otherwise, viral takes it own sweet time to recover.