My dog has a swollen leg and other symptoms.?

Hey, i have a Pitbull, i left for vacation and left him and my other dog for a week, when i got back , i noticed he has a swollen back right leg, which is kinda red, he has both ears in the inner part hurt and red. his whole right leg is swollen from top to bottom and he has like blisters and stuff all over , what could this be???? THANK YOU SOOO MUCH :;((((