You did the right thing to call the vet when you don't know. Foot lamenesses with heat like that can be laminitis which is quite serious and can be permanently damaging.
In your case, he sounds bruised if the vet found no laminitis or abcesses. Most horses that have been shod don't do well barefoot, is there a reason you are trying to go without?
I have read articles that barefoot is better...also I was trying to save some money...I thought because he's not outside all that much in the winter that it wouldn't matter.. I guess I was wrong.