Feeling pin pricks on skin occurs on the heels, the finger tips, and sometimes on the inner thigh and the mid back.
This is a feeling one gets when usually the tips of the nerve endings misfire for seemingly no reason. Muscle fatigue may have something to do with it. Sometimes there may be some inflammation such as the feeling of pin pricks in toothaches. However, most of the time, the feeling of pin pricks on the heels and skin does not indicate inflammation of the nerves.
It may be the misfiring of the tips of the nerves because the muscles are tight and somehow the neurons are fighting their way to the end through the tight muscles.
I sometimes feel pin pricks on the tips of my fingers although I cannot remember any event or situation that would have triggered the feeling.
The one thing that I have noticed is that if I type a lot, which I constantly do, and move my fingers a lot, and if I keep my hands and fingers warm, I do not seem to get pin pricks on the tips of my fingers.