You're right, your pain could be coming from a muscle.  It could also be coming from a joint, a ligament, a tendon, some fascia, a bone, a blood vessel or just about any deep tissue.  In reality, 'classifying' your pain adds nothing to your healing process, but having a clear nerve system does.

Tissues devoid of animating Life cannot repair or heal.  Cut into a LIFELESS steak (a muscle), and it will never mend.  Injure a LIVE body part however, and it will reorganize itself successfully as long as it receives 100% innate intelligence from the nerve system - regardless of what sensation you feel.  When that power of Life flows - you heal.  When it trickles - you don't. When it stops - you die.

As Chiropractors, we have compassion for any discomfort you present with.  But realize, while naming your 'tissue of pain' (diagnosis) may provide some peace of mind... detecting and correcting the cause (adjustment) will restore your health.  For us, what hurts is not nearly important as what's Subluxated.