Phlegm in babies

My 1 week 10 days old baby has been sneezing a few times last 2 days and now when he sleeps i can hear sounds at the back of his nose/throat like phlegm blocking his nasal. Went to see doc at poly and was given saline drops to insert in his nose every 6 hrs. Should i continue doing this or should i return to a doc and get them to help clear the phlegm? It pains me to hear my LO breathing with some kind of obstuction in the nasal area.