Good Pain v. Bad Pain

My physical therapist has turned me loose, though I have 30 days to go back without having to get a prescription for it.  (Which I find it really odd to have to get a prescription for physical therapy, but that's another story)  So, my assignment now is strength-building and exercise, but without overdoing--which I managed to do in less than 24-hours.  I'm allowed to push a bit, and we discussed "good sore" versus "bad sore."  "Good sore" is just tired muscles or stiffness.  "Bad sore" is swollen back muscles (which I've only managed to do once) and/or strain or sharp pain.  Yesterday I sort of fell between the two, so if one looks at it a certain way, I've only half overdone.  That's something.