I had it really badly in both heels, and still do to some degree. Reached the point where I couldn't walk to the shower in the morning and they were sore all day.
Saw 4 different physios and 2 podiatrists, and eventually it was put down to the way my feet hit the ground when I run/walk. I was given several simple stretches to do every 2 hrs to start with, and now do them twice a day. I also have special insoles to wear in all my shoes to reposition my feet. Cost me 400-500e to get it sorted as I ignored all the early signs ant let it become a major issue. In the end I went to the physio in August after preseason rugby training, and played my first game in early March, after starting training after Christmas. I was however told that cycling was not an issue and used it as cardio as I couldn't run
I would recommend finding out what the cause is, as it wont just go away on its own.