It's really hard to make toddlers eat veggies especially if they've been accustomed to eating tasty and sweet stuff. I guess all you have to do is just keep on offering, or if that won't work, try disguising the veggies into what he likes to eat. But I suggest you work first on my first advice. That way, he'll know he's actually eating veggies and who knows, he might learn to eat other healthy stuff too?