My 2year old baby boy poop small hard balls,should i be concerned?

Define "concerned": This is certainly not uncommon or suggestive of a bad disease. It does suggest the need to add non-constipating agents like fruits (peaches,plumbs,pineapple,pears, etc. ) to the diet. Avoiding known constipating agents like apples/applesauce/breads/rice/bananas would also help. Prune juice is a natural loosening agent that could help within a few days.