I don't worry now but when my ds was 18 months old, he hated any veg, fruit, mash potato (or even chips ), pasta, anything remotely healthy or fresh! He would occassionally nibble on toast, eat yogurt from a tube, never with a spoon , sausages, crackers with spreadable cheese, chocolate raisins and that was it!
Don't stress at all, the more of an issue you make it the more he wil rebell.
DS is now 2.10 and although is still anti veg, he will occassionally eat carrotts, he does eat apples, grapes, oranges and fruit smoothies. Cereal, potato waffles, he loves fish- especially salmon, pasta in tomato or creamy sauce, cheese, chicken, gammon, baked beans, any sandwiches which he would have refused before, yogurts, with a spoon!!!!!
We just had to ignore him completely when he refused to eat and just not nag him, the more we nagged him, the more stressed he got and the less he ate.