I remember being so happy when I got a blister while training: it gave me a chance to try out my blister remedy ideas! I had plenty of blister prevention ideas that had been keeping me blister free for months. May I suggest you use this opportunity to see what you might do to deal with a blister other than limiting your walking, which may not be a good option for you when you are on the Camino? I had good success using a hydrocolloid bandage. Some brands are 2nd skin (my favorite because it is so thin), Band-Aid, and of course, Compeed. I carried little alcohol pads (the type people use to prep skin for injections, available very cheaply in most drug stores/pharmacies) and prepped my skin with those to ensure good adhesion. However, I strongly suggest you try them now if you are considering them because some people really hate them!