I found stretching my Achilles tendon by standing on the stairs on my toes and lowering ankles down slowly and holding for a few seconds and repeating helped. Should find a better description online.
Also rolling my foot on a golf ball.
I would also recommend seeing a physio.
All good suggestions - definitely see a physio or a podiatrist if you haven't already. I found rolling a frozen orange under my foot really helped relieve the pain - you can pop it back in the freezer after use so it's ready for next time.