Toddler Cough

My son has had a cough for a week and a half now. We were both down with a cold last weekend but got over it. However, his cough has continued to get worse over the past few days. He is getting molars and has had a runny nose but no fever at all. Is it worth it to take him to the doctor? Will they even do anything for him? It's not constant but he gets really bad coughing spells several times a day. He run a humidifier as much as possible and give him Zarbees when it gets really bad. any suggestions?