Don't worry. All you need to keep an eye on is whether he can follow your instructions. For example, you can ask him to "come to me." If he walk over, he understands you. That's good enough. Keep talking to him, he will eventually open his mouth. My daughter could say only about 10 words when she's two. When she started talking around two and half, she talked in complete sentences. Now she's eight with an IQ over 130 and reads at 5-6 grade level.
