Toddler smelling food

Okay.. so google has driven me crazy. Does anyone out there have any advice/insight on my 2 1/2 year old son smelling any food before he eats it ? Well. Let me rephrase that, he doesn’t eat anything but fries, pizza, Mac n cheese, welches gummies, mandarins, and grapes. Literally that’s all! He smells any food I try to give him, and Ofcourse doesn’t eat it. I also notice sometimes during the day he’ll touch stuff as well as myself and his dad and smell his hand afterwards. Anyone have any suggestions or help or experience with this ??