What you are experiencing is a simple case of a blister albeit a large one. Blisters are a natural occurrence to frictional pressures on a part of the skin that is extremely soft and not used to these kinds of forces. Some of the most pressure sensitive areas of the skin are the palms and soles of the feet. These also started out as soft areas but over a period of time and gently getting accustomed to pressure have hardened to a point that they are not affected by the pressures and friction imposed on them. The problem that you are facing cannot be cured immediately. What you need to do is to simply leave the foot be and wait for the blister to go away. The end result will be a callus, which will also go away in time.
The skin on our bodies is slightly different in the areas where there is excessive force of pressure and friction. These are unnatural conditions for the skin to be in and whenever the skin is subjected to damage from these, it protects itself from further damage by a layer of hardened skin. The normal human skin consists of a layer called the keratinocyte layer. This is a layer of skin cells that have lost their nuclei and only contain the waterproofing skin protein called keratin. Effectively, these cells are simply storage areas for keratin. This is a hard and tough layer that is especially concentrated in the soles of the feet and in areas that have been subject to frictional forces. This transformation of normal skin to a more keratinocyte rich skin happens with injuries like the ones you went through. This injury causes a layer of serous fluid to come in between the existing top layer of skin and the deeper layers beneath; preventing further injury. In time, as the skin heals, the serous fluid will then be reabsorbed and the remaining skin collapses and hardens. If the pressure forces that caused the initial injury still prevail then the skin will completely harden over. Otherwise, the hardened skin will simply return to normal later.
There is nothing that you need to do about this problem other than to ensure that the blister does not burst. If this happens, bacterial infections won’t be far behind and on a wound this size, could end up posing a serious problem to your health.
answered by G M