You cannot make your son eat. He must decide that for himself. Keep a regular schedule for meals and snacks. Don't allow your son to make you a short-order cook. Avoid serving snacks close to mealtimes.
New foods seem most attractive when a child is hungry.
Make no comment whether or not your son eats the new food. Then he may decide to try it on his own. If he does, begin serving the new food on a regular basis. Invite your son to help prepare meals. Children are more likely to eat foods that they have helped prepare.