R.S.
He isn't hungry. Children will eat if they're hungry, and if they're not they'll play or get the stuff they don't want out of their way. If he's eating well at daycare, he's probably getting enough that he just doesn't want dinner, especially if they have an afternoon snack.
First, make sure the daycare snacks and lunch aren't all cookies and gummy bears. If he's getting fruit, veggies and whole grains along with milk at daycare, he's fine even if he never eats dinner. Second, find out what time the afternoon snack is given (my kids in kindergarten were often given their snack right before dismissal and didn't want lunch.) If the snack is cookies or chips, etc., either provide him with a more nutritious snack, or ask them to cut his portion way down so he's not eating so much late in the afternoon. Then, only give him two or three bites of whatever his dinner is, maybe one bite of meat, a couple of green beans, and a chunk of potato. There's less to throw in the floor, and with less to choose from he might not dismiss it so quickly.
Also, if you're giving him milk or juice in a sippy cup or bottle on the way home or when you get home, start giving him water instead, or water down the milk or juice. Lots of kids fill up on liquid and don't want dinner. And give him water or a very small amount of milk with his dinner so he doesn't just drink that and get full.
You might try the book Feed Me I'm Yours, which is an excellent guide to how much a small child needs to eat (surprisingly little.) It also has good recipes and suggestions on feeding toddlers.
Last, unless your child is losing weight, don't worry and don't make an issue of eating. Children will not starve if food is offered to them and they're hungry. They might hold out if they don't like something, but very soon they'll eat. And if they're offered a wide variety of healthy food, they don't need butter, sugar, salt or other "sauces." They'll learn to like healthy food.
Just so you know, I'm not a health nut. I'm a school cafeteria manager with three kids and my own bad eating habits. But when my kids were little I started making grilled cheese without buttering the bread, and they love it that way (mine drips.) I started giving them whole wheat bread and they don't like white (I had to teach myself to eat it long after they learned.) When I took over the cafeteria at school, I quit deep frying anything, took the butter out of the veggies, and started offering more raw foods and whole grains. I have more kids eating lunch now than they had under the old system. The teachers don't like it as much! But the kids are learning healthy eating habits that will last all their lives.
Don't worry! This too shall pass.