If you are concerned that he is behind other kids his age, it doesn't hurt to discuss this with your pediatrician. If he's just a little behind, it's probably just fine and he'll catch up on his own very soon. If it's more significant, it's probably worth it to get a referral and an evaluation by a speech therapist.
I took my son for an evaluation at 2 years. He was definitely behind. We also had his hearing tested, just in case. At 2 years he was really too young to work with the therapist, but she gave me some great tips. Took him back at 2 1/2 years, and he was still behind but old enough to begin going to speech therapy. When he turned 3 we started taking him to the local grade school. He's 7 and doing great!
The reason I would consider taking him to be evaluated is to rule out things (like hearing) and also because not being able to communicate is frustrating for you and for him and will hinder is growth and development is other ways.
It's possible he's just a late talker, but if there is anything else affecting his speech, the sooner you identify it the sooner you can help him and get him talking and learning and developing.
I think some people are well meaning when they say, "Oh, my son was a later talker, too. He'll be fine." But what they are really saying is, "Don't worry. He'll talk some day." But I didn't want to wait for some day. If I waited for some day, my son would have had so much more frustration and so many behavior issues and just so many things that we would have to correct and undo. Speaking is a huge part of their development, and if they are delayed in their speech, they will be delayed in many other areas as well.
It doesn't hurt to talk to your pediatrician and have him/her check him out and ask a few questions.