You need to talk to your vet before you give him anything. Just call the vet and ask them. I never heard of giving Echinacea to a puppy and if your vet told you to then he also would of told you how much. I wouldn't give it to him!!!!!
He could have a splinter/thorn in it. It sounds like his paw is hurting. He could also have fractured a bone. Take him to the vet.