I don't particularly trust the medical services here in China if I can help it. In this case, they'll almost certainly give me Traditional herbal medicine or acupuncture which I just don't buy into. Failing that, painkillers which I already have.

I'm a little less sure the intercostal thing is the accurate description now but your 'serratus anterior muscles' looks more locally accurate! Especially last night where the strain kind of migrated round the back making sleep way more difficult. (overall, things have improved though)