Yikes! Blisters are no fun.
I have to admit, we dont have the Scarpa Trek Pro in the United States. They look like a moderately hefty boot: all-leather one-piece uppers, fabric (Cambrelle) lining, and a Vibram sole. So its possible you were a bit hasty in taking them out for a two-hour-plus hike without trying some shorter walks to expedite break-in. Im assuming they fit well. You dont want boots to be sloppy in the heel, but neither do you want them real tight and creating pressure points.
So what to do? Check your sock combination, for starters. I always suggest a light liner of Coolmax or other material, with a mid-weight wool sock such as the SmartWool Light Hiker (US$15). So try that, and once you heal try some shorter walks (less than an hour). If youre still getting hot spots, you may need to find a bootsmith who can re-shape the heel area a little, creating more space. But that probably should be seen as a last resort.
Your other alternative is to simply do what you can to prevent blisters, using Moleskin or a similar product to create a layer over the skin that can absorb the friction. That stuff works well, but these days I hate to use it as boots today fit better and usually dont require heroic measures to prevent blisters.
As for blister treatment, avoidance is the best cure. If I do blister, I prefer draining the blister with a sterile needle, then building up an area around the blister with adhesive tape or other products that help keep the boot away from the affected area. Keep in mind, though, that breaking the skin over a blister can lead to an infection. Products such as Spenco Second Skin also help protect and cool the blistered area.
Otherwise, wait a week and they heal right up!
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