My son (2 and a half) has had a on going cough for 3 weeks. It kinda comes and goes but it's bad…

My son (2 and a half) has had a on going cough for 3 weeks. It kinda comes and goes but it's bad again to where he is up all night. No other symptoms still his normal playful self. He has asthma. Do you think it's time to take him to the dr?