Where were the blisters located? It may well require a trip to the vet to determine the root cause of the blisters in order to cure it.
In the meantime, follow Andy’s advice with a 1:20 dilution of Betadine, applied by immersing for five minutes or using cotton wool ball to clean and irrigate for the same length of time. Do this twice a day and see how you go. If you have access Flamazine cream, this can be applied during the periods between bathing the sore.
Blue