chesty cough

My baby is 7 week old and Thursday morning he woke up with a really snotty nose, it wasn't running you could just hear all the mucus in his nose when he was breathing. Friday night he started with a cough and it's been sounding really mucusy. It's not a bad cough but I just don't like it. Should I take him to the doctors or is it just caused from the cold he has had and will go away in time?