Pain that stays often has a job it believes it is doing. It keeps the record. It proves the thing mattered, that you were not making a fuss, that somebody ought to have to know.
Which is why feeling better can seem faintly dangerous — as though the ache were the last remaining witness, and letting it fade would amount to agreeing it was fine.
It would not. The record can be kept somewhere other than in your body. You are allowed to know exactly what happened and still stop carrying it in your chest at four in the morning.