We have had similar issues with Ryan since he was 15 months. Introducing new foods is a nightmare as like your DS he won't even try them .We have a refluxer so there are other issues thrown in the mix with us but the advice we have been given may work for you .
Here's what we were told .It's all about them being in control and they like that , you have to try and turn it around so yes they still have control but so do you ! you are meant to put the food in front of them and say no more , don't emphasise on the feeding issue like " come on eat your lunch " "one more piece " that sort of thing , just leave it there , if he plays with it , that's o.k .If he doesn't eat it you say " are you finished ? o.k i'll take it away then " then you let him see you put it in the bin .you don't offer anything else only a drink .The next meal do the same , if he doesn't eat you bin it .soon he will realise that he isn't getting choices and if he doesn't eat he gets hungry .
Obviously you can't expect him to eat something he has never had straight away , so in the meals you offer put at least one food you know he will eat . If he has refused food all day then give cereal before bed . It does sound very harsh but it supposedly does work .We are working on this ourselves as Ryan is a junk monster.
With Ryan we can't leave him without before bed as he has reflux and this will be worse on an empty tummy .You hear it all the time children won't starve themselves they will eat if they get hungry , with us if Ryan refused to eat a meal we got concerned and offered him replacements , anything just to get him to eat so he wasn't getting hungry .
We are waiting to see a dietician as Ryan does have swallowing issues due to his reflux so it's a bit both here , he won't try new foods and he's scared of swallowing incase it hurts.
also you could try putting the new food on his plate a few times , encourage him to play with it , put it to his mouth , chew it , swallow it .To get Ryan to taste something we encouraged him to kiss the food , then lick it , then try chewing we haven't got to the swallow yet but at one point he wouldn't even touch it .I know your DS is a lot younger than Ryan but thought i would share the info i was given with you as i know how frustrating it is .Just try not to show him that it's a big deal he's not eating , they do pick up on it and they know they are in control .Believe me Ryan has very few foods he will eat , apart from junk/snacks he will eat about 10 foods