Suggest Treatment For Cold And Chesty Cough In Child

i have a 6 week old baby he has had what seemed like a cold for the last couple of days and seemed alittle chesty but today it seems really bad and he has started sounded like he has a crackly chest and you can feel it as he is breathing i am going to phone the doctor tomorrow but is there anything i can do to help him tonight please can i have some advice thank you