i think you two are talking about the same thing. whenever that pain in the jaw happens to me after i yawn, it doesn't really feel like a "pop", it feels like some tendons or muscles got cramped/tangled or something (like what he's describing). and when i feel under my chin there's a hardened area, as if there's some muscle there that's flexed.
it's nasty as fuck, but the worst of it only lasts for less than a minute. the rest is just residual pain