How do I know when it is time to make an appointment for a sports massage?

It's never a bad time to book for a massage, obviously, if you know that you are due for one because your body is telling you so, then don't wait any longer.

Bear in mind that an upper back pain between the shoulder blades will take a few weeks to resolve.
at first, it would seem that is getting better, but it doesn't really go away. that's a good time to see your personal massage therapist.

If you have a lower back tightness, it may be a call from the hamstrings which normally don't give much trouble, but they do get very tight and pull on your hip bone.

Are you knees sore? that could be your hamstrings if at the back or your quadriceps if at the front of the knee; that means, you need to find time to give your legs a break by having a deep tissue massage.