Hi Aggie
Once, a long time ago - well before I was diagnosed with SLE - I used to get a pain in my heel too. Whenever I lifted my heel off the ground, it almost felt like there was a weight inside my heel and it was knocking against my heel.
It went away eventually and I have no idea what it was or what caused it, so I'm not sure if it is useful for me to post this at all! It definitely wasn't caused by new shoes or extra exercise.
Obviously, I have no idea if your pain is the same as mine was - but I thought that you might find it comforting to know that other people have had bizarre aches and pains too that have just appeared out of the blue
HTH
Nellie