There are a number of tricks you can try to get him to eat veggies- from as subtle as pretending broccoli stalks are "trees" to the other extreme of completely hiding veggies in recipes, smoothies etc so they don't even know they are there.
But, personally, I think if he is eating balanced everywhere else and/or getting vitamins from other sources, you should just watch and observe for a while and see where it goes, while still trying to occasionally push the veggies. At 3 years old, he is finally solidifying his likes and dislikes, and his taste buds are getting fully developed. He's just like any other person, there are going to be things he loves and things he dislikes- period. And those may not ever change.
LO's likes and dislikes in food do change over time, but it often happens much later in childhood. Think back to yourself and all the examples of things you hated that you still have, or conversely, all the things you hated that you now love...