This might not be what you want to hear... but what if you gave veggies a break for a while? Loads of toddlers and pre-schoolers won't touch veggies, and it just becomes a battle. Most times the nutrients in veggies can be supplied by something else. As long as his diet is good he will be fine - some cultures (eg Inuit, Masai) don't eat veggies at all.
My DS1 wouldn't touch veggies from 2 till 5 and even now I have to coax him.
If you give him somthing new, I would just give him to TINIEST taste so there's nothing left to throw.
