His taste buds are changing. You can be a dictator at dinner time or you can make life easier and not give him a food fixation that will last the rest of his life by helping him find words to tell you what's wrong. Then try to help him find foods he likes.
You don't have to make a meal and order him to eat. If he doesn't he will go hungry and he won't eat it later because he won't like it anymore later than he did at the meal.
I found out the hard way. I became a tyrant and would make our girl try everything on her plate. She'd even puke sometimes. I didn't care because darn it, "I'd" worked hard to make that meal and it was just fine. She didn't get to disrespect me, no sire...see where that went? It became all about me and nothing at all to do with why she'd stopped eating food.
Come to find out she had Geographic Tongue. Her taste buds would change around and do weird stuff. You can google it. Yes, her tongue would look like she'd splattered boiling water on it and the blisters had popped.
She went without eating as long as I'd try to make her eat food she didn't like. She got so bad one time that she nearly ended up in the hospital.
I stopped and said I'd had enough. That "I" did not have to be a dictator and that she was a human being and could make some choices.
So she gets to be very much a part of the meal planning. But even then, sometimes she will look forward to a certain meal and when she takes that first bite she gags and pukes it back up. That's not choice. That's something different.
People say I have her spoiled and if I'd just make her eat what I fixed a few times it would all be over and she'd be eating everything I put in front of her.
That's not true. There are times when we go to McDonald's and get her a nugget meal, her favorite meal ever!, and she gags and pukes it back out.
It's not a choice and her having some nutrition in her body is way more important than my ego.
So don't let your ego get in the way of your child needing you to listen and help. If he's not wanting to eat it and he's trying and it's not working then obviously you just have to try other things. There are times when our girl only eats a PB&J for lunch and dinner. She'll almost always eat cereal for breakfast but sometimes she just can't eat at all that early.
Compromise and working through this is important. Take him to the pediatric dentist too, they can examine his mouth to see if he has teeth coming through or maybe even Geographic Tongue.