I'm seeing this more and more in my work. If he has only eaten jar baby food you can't blame him for being a bit confused.
Is he still being sick after meals? Is he still get some reflux?
He needs to get hands on with the real food, so lots of messy play with cooked pasta, raw/cooked veg, jelly, cereal...lots of different textures, you get the idea.
If you have a play kitchen the you can role play with play food e.g. cooking, serving and eating it.
Lots of stories about food...log to the library and look at gardening books at different vegetables. Visit a local allotment, some do sessions for toddlers.
Get him involved in putting food in the trolley when food shopping.
Very importantly sit down and eat in from of him so he learns that you trust and eat the foods so he can too.
Don't bribe with chocolate/ice cream etc. as it has been shown to make the food you want them to eat less desirable.
Never force feed. Don't pressure to eat.
Offer little tastes along side the normal jars food. Make sure he portion sizes are the correct amount as this can be very off putting.
Make sure he is not having too many snacks too close to mealtime or is drinking too much milk before meals.
Ensure he is receiving the recommended multivitamin for those under five years old. Mainly vitamins A, C and D but many brands will provide a lot more vitamins.
And be realistic and adapt your expectations, he isn't going to eat a whole roast dinner in the next week. It will be very slow, steady, consistent steps from you and all family members.
Best of luck