My dog has a swollen leg what can it be?

my dog has a semi swollen leg and he always nips at it so i took him tot eh vet and the vet took a skin sample to make sure its not mites and it wasnt . she said he had allergies and gave me some medication ... well i gave him the meds but he still nippd at his leg and now his leg is super swollen... ive pulled on it and poked it to see it it hurts him but it doesnt... he doesnt seem to be in pain he walks/jumps fine but the leg is about 2 times the size of his other...what can this be ???

Find another vet and take him in immediately. The nipping means your dog is in pain. Allergies will not cause one limb to swell as you have described. A skin sample does not show possible infection which is what this sounds like. Please get the dog back in to another vet asap.

It sounds like something bit your dog, possibly a snake or a spider. Take him to another vet and have him checked out.

Injury or infection

I would take it to a different vet, sounds like a bee or wasp sting or could be a snake bite