I am just getting over what I think was achilles tendititis, pain in the back of my heel. I'm pretty sure the cause was not anything I did. Years ago I ripped my other achilles and I know what that feels like; this was different. Eventually RICE (rest, ice, compression, elevation) made it better . An ankle brace kept the swelling down. It's almost gone now, after almost a month. Good luck, and be patient.