If your 3-year-old child has been coughing a lot for the past 2 days, there are a few things you can do to help. You can try using a humidifier in their room to help with congestion, elevating their head while they sleep, and giving them plenty of fluids to stay hydrated. If their symptoms persist or worsen, it would be a good idea to consult with a pharmacist or healthcare provider for personalized advice.