What Causes Sharp Pain Right Around The Point Where The Achilles Meets The Bone?

Question: Hi. I'm a 39 year old male and keep in very good shape. A few weeks ago, I was stretching and went into downward dog, which I've done hundreds of times before. Except, this time, when I tried to push my left heel to the ground, I had a sharp pain right around the point where the achilles meets the bone. Eventually, by continuing to push a little bit at a time, I could get it down. But, a couple of days later I'd try the same thing and it would hurt again. As I started to read about achilles issues, I found that forcing a stretch like that can be bad, so I'm not pushing it anymore. It doesn't really hurt during most activity (walking, light running, other stretching, etc). The only times it hurts is when I try to do something that puts that left foot into dorsiflexion (like walking up a steep hill and letting that heel drop, or doing a wall stretch with that left leg back and straight at a 45 degree angle or so). Otherwise, it will sometimes feel "twingy", almost like there are little bugs moving around in my ankle/heel or like something is rubbing. I'll also sometimes feel it when walking when my leg/foot is fully extended forward (like, if I kicked my leg forward beyond a normal walking kick, I'd feel that sort of twingy, non-painful feeling...). I've stopped running, jumping rope, box jumps etc because I'm worried about aggravating it more. I'm doing some gentle, non-painful stretching and some eccentric heel drops (but not below flat so I don't go into dorsiflexion). But, then I'll be doing something like going into a pushup position and I'll push that heel back a bit just as I'm doing the pushup and I'll hit that pain point again. It's frustrating because I don't know what I should or shouldn't do to make it go away. I've really only been trying to exercise and gently stretch it for the week, so maybe I just need patience, but I'm not sure if I can run at all or if I can do things as long as they're not painful? From what I've self-diagnosed, it seems like it could be insertional achilles tendinopathy. However, it doesn't bother me in the morning, isn't really stiff, and I can't really manipulate my achilles manually in any way to cause pain. It almost feels like it's "behind" my achilles...like a nerve rubbing against the bone or something?

Anyway, hope you can offer some insight and advice. Thanks!