I went around and around with this issue with one of my 17-year-old twins.
I mean, we tried everything from age 2 up to 6th grade. He had some expressive speech issues at age 2 and 3, but he also ate only a few foods, and I really let it stress me out. It caused problems when we would eat at relatives'' houses. The grandmas could not resist offering every food under the sun. We would have some strange combinations at Thanksgiving!
It affected his social life a little bit in elementary school when every birthday party had pizza, which most kids love but not mine! But he handled it. He just sat there and had fun without eating.
We saw speech therapists, two psychologists, a behavioral specialist, an OT, and everyone in between. When he turned 13, I even forced a local doctor, who is a nationally known expert on tween and teen eating disorders, to evaluate him. He was straight with me and said, "I don't see a disorder. Some people are picky."
I'm including all this just to say that a LOT of changes are taking place during the toddler years, and not everything is a diagnosable problem. Some stuff you both just have to get through.
One thing I KNOW does not work? Forcing his hand. Offer SOMETHING he likes at every meal. Every kids is not going to eat a food pyramid-worthy meal every time. Heck, most ADULTS don't do that!
Don't make a separate meal for him, but don't FORCE him to "eat it all or don't get up from the table."
A lot of "picky eating problems" are really just problems with parent expectations. If my kid wanted to take a hamburger bun, juice box and cheese stick in his lunchbox, I finally learned to let him and then let him make up the difference when he came home. Sure, it didn't SEEM like a nutritionally balanced, bento-box type lunch. But it got him through the day until he could get home and eat something he really wanted.
The funny thing is that now he is the most adventurous eater in our family of 5. He loves spicy foods, sushi, raw oysters, etc. He won't eat ketchup or maple syrup. But he gets fed, takes a vitamin and is healthy.
My point is that this age is confusing for parents as kids develop motor skills, language skills and emotional expression. Take it slow and be as patient as you can.