hey ladies, i need some advice.

so my boyfriend has a 3 year old son and we’ve been trying to get him to eat regular food for months now but he refuses and throws huge fits. all he will eat is chips, jello, and his mom feeds him kids meals from mcdonald’s but he will only eat the nuggets so he can have the toy. i finally put my foot down and told my boyfriend he needs to eat healthy food. nothing we offer him works. he won’t even eat chicken nuggets we make in the oven. everything is a no-go. mashed patotos, sandwhiches of all kinds, soup, spaghetti, you name it, he won’t eat it. has anyone had to deal with this and what did you do to help?