4 week old baby with virus?

my 4 week old baby has caught a virus(runny nose and cough) from my 1 1/2 year old son.. She just seems to be congested and coughs a bit, which could just be the normal newborn cough.. I am using nose spray and sucking her nose when it needs it.. The doctor said that there is nothing they can do for her and dont need to see her... she doesnt have a fever or anything like that.. Is there anything i can do for her? i dont want her to get any sicker? Is it normal for babies this young to get colds?