no, I wouldn't be concerned, but if you are, take him to a doctor to get checked out. He is only 23 months old. Some kids don't start talking until they are 2 1/2 or 3 yrs old. There is such a wide range in developmental milestones. Don't go by the books, either. My son didn't start walking until 19 months!! And he is normal. Don't go by me 100% because I never actually saw your son, so it's worth getting him checked anyway.