My Lo Is About 7 Weeks And Last Sunday We

my lo is about 7 weeks and last sunday we brought him for a check up because of cough but no fever..the dr checked for phelm but none.. she just gave something for his nose(forgot the name) and didnt gave meds for cough since ny baby is too young..she just advised us to have him nebulized.. but up to now theres still a cough esp. when hes sleeping on his back but not persistent but with side lying hes not..he still active and finishes his milk.. is this something to worry? do i need to go for follow up check up? thanks!