He's such a fussy eater :/

Hi, I have two boys, my 2-year old Joel and my 3-month old Eoin, Eoin's being good as gold right now (for the most part :P), but Joel is being such a fussy eater! Literally anything that isn't fish fingers and/or chips will either be left on the plate, be thrown on the floor or spat back up, at my wits end trying to introduce him to other foods  any advice??