i agree with jimoinycricket - dont let food be a major issue. Put his nuggets on a plate with some white bread and a couple of other items...some peas, a carrot stick.
(get fun books like the chatlie and lola one about not eating a tomato.....)
SOme days just put plain chicken on his plate with white bread. But dont fuss about it, just do it.
sit and chat about your day with him or sit at the table as a family ignoring him not eating, but prasising any attempt to try something new.
Maybe try something new for all of you...like beetroot or artichokes or some strange new fuit. SHow him its OK to try something new and say what you like/dislike. You could have a good game with that. Who will get the last slice of nectarine,,,,
ALso have fun with your food....pizzas made on english muffins in the shape of a lion. Catapiller fruit kebabs.
Use books about food.....the hungry caterpiller for example.
everything is so new for him, he will still be finding his way, so all you can do is nuture and let him develop risks in his eating.
Ask him to help plan the menu for the week...you might find there is more that he likes if you suggest things...like pasta, fish fingers, beans, sausage rolls, ice cream, jelly, cake.....