Many children are simply afraid to eat new foods. It may take many occasions of you putting vegetables on his plate before he'll even touch them with his fork, let alone put them in his mouth. (And you’ve already heard that you shouldn't force kids to eat anything; otherwise mealtime just becomes a power struggle.) Hang in there, though. After a while, he'll want to know about this mystery food and give it a try.
In the meantime, have you tried disguising veggies in the form of other foods? Make him a smoothie, er, "milkshake" with the berries he loves — but also with pureed carrots. Use your food processor to whip up some mild homemade salsa with tomatoes, onions, green peppers, even zucchini. Puree squash into pasta sauce for his spaghetti.
Finally, remember that your toddler looks to you as a mealtime model. If you eat healthy, odds are good that he will too.