I've had this. It was called tendinitis back then.
The test for it is to squeeze the achilles tendon. If there's a point that makes you go "Ouch", that's what you've got.
The standard rehab protocol is heel raises and lowers to a stretch. I did that for quite a while, but got bored with it.
I was told that it was oaky to do regular activities with the condition, but to avoid running up hills.
Basically, it just went away without much intervention. I get the feeling that the 'rehab' is another of the placebo things that physiotherapists hand out.
I'd suggest not doing the stuff that hurts it. Check that it isn't something like the back of your shoe touching and causing an irritation.
Stretching the calf muscle could help a bit and it probably won't hurt to do a step raise and lower with a stretch at the bottom. three sets of ten is as good as any combination, as far as I know.