Fussy eater

My 18 month old has always been a fussy eater but now he will literally point to his snack cupboards, eat them no problem, but actual meals, it’s ALWAYS a battle. So I know if he was starving he would eat but at the same time, he’s just started nursery, and he’s going ALL day without eating anything at all! Get home for dinner, trying him with actual dinner first, and he’s still only eating it a little bit but if it’s snacks, eats no problem! If he doesn’t eat his dinner, are they still too young to offer them something else a little later on, so they’re not hungry? I’m always so worried I’m doing the wrong thing! I don’t want him to not eat anything at all but at the same time, I don’t him to have something in his belly? Anyone else the same? Anyone have any tips/what to do? I’m so stuck!!😩😩😩