The level of pain I had initially after the injection was "not usual, but not a problem. In fact it's good b/c it means that your body has a very good inflammatory response and it should heal very quickly.", according to the doctor.
It's now been a little over a week since the injection and I could walk normally, zero pain unless the foot is in certain positions which aggravate the tendon on the medial side of the foot, which is what was injured originally.
So what do I think about PRP for my situation? Still not sure yet... I'm going to give it about another week or two and see how I feel. But after reading some of the actual published papers on PRP, I'm not as "optimistic" as I once was just hearing it from the doctors. All the places that do PRP make it sound like a miracle for every kind of pain in any kind of joint, without regard to it's cause, duration, specific reason for the pain.
The guy I went to didn't seem to care that much about figuring out exactly what was causing the pain or suggest imaging or do a more careful evaluation first before just recommending an injection into the parts of the ankle that caused pain. So I was a bit unsatisfied in that regard. But ultimately, in a week or two if I'm completely back to normal (pre-injury), it means that the PRP was beneficial and I'll be happy with that.
BTW, in a news story just a few days ago, Nadal announced that he just started a "new type of treatment" for his knee. I'm pretty sure that it's PRP and/ or stem-cell therapy.