A condom or plastic of some sort would probably just make the dogs paw sweat, so perhaps just a nice thick bandage with a sock over the top....oh and use some of that medical sticky tape stuff at the top (assuming you have a short haired dog)....Pooch will probably use the bandage to entertain herself with the challenge of taking it off.

I would then take it off, but only when you are around a: to stop her licking it once the bandage is off and b: to let some air get to it to help it dry out.

Hope it heals soon! Pats for your poochie!