I agree with Mike on this, rest, rehab, shoes is key. DO NOT RUN THROUGH THIS. ICE 20 minutes on, 60 minutes off while acute, 2 cycles max, while acute.
I would also look at nutrition, make sure you are getting enough Vit. C, Ca, Mg, GAG's, Bromalain.
If really bad and you want to be agressive, use a posterior splint to keep your foot dorsiflexed (calf stretched position). No longer that a couple nights or so. This will keep your achillies at the maximum length overnight when new fibers are being laid down. (usually we sleep with our feet pointed, first step rips all the new fibers or at least damages them).
Acute modified training- No hills, no jumping, no speed training, walk on soft surface (trail), slowly increase training to tolerance. (you will know the next day.
SubAcute- likely after 1 to 2 weeks- alternate hot cold. (heat before exercise, cold after. See mike's notes above.
If that does not work...?...
Don't get a steroid injection, apparently it is risky. Good luck.