I occasionally walk a long way and find that the tendons in my foot become sore, especially the one tendon that leads to the big toe. When I get home and take off my shoe, the skin right over the tendon looks a bit raw and inflamed. I don’t think the shoe or sock is abrading my skin, so why would an internal thing like that manifest itself on the skin outside?
If the skin really is raw, I’m pretty sure you’re getting some abrasion from your footwear. And I don’t know why walking in shoes would cause pain in that area of the foot if there were no abrasion involved…
For many of us the skin over some tendons, especially those in our hands and feet, is extremely thin, and I think that is why inflammation of a tendon can affect upper layers of tissue and even the surface of your skin. Inflammation is rather a funny thing and can cause surprising physical changes to areas you’d think would be unaffected by strain, trauma, etc.
I am recovering from a tendon injury and surgery on my hand, and part of the healing (and therapy) process has been tenderness, redness and swelling of the skin over the affected tendon, often quite far away from the actual site of injury/surgery. There is a part of my thumb nowhere near my scar that is more tender than my scar most of the time, and even gets some small hives every once in a while (hives/non-traumatic skin swelling are a typical problem for me personally with injuries) - I think the stretching of the tendon when I do my phys. therapy is most intense there. Doctor says this is entirely normal.