My son is one month old yesterday. He has a really bad cough and a stuffy nose what can I do for him?

You can take him to the pediatrician. At one month old you need expert advice rather than advice from strangers on the internet. For the time being, until you get into the doctor today, go into the bathroom, close the door, and run the hot water full steam. Hold baby in your arms while sitting in the bathroom. Let the steam in the room build up. When the water turns cold, turn it off, but stay in the bathroom until the steam dissipates.