Can be either.

Can also be an Adhesion. That's the "sticky" substance that develops in and between muscle fibers sometimes; as a result of injury, tightness, or inactivity. It binds the muscles together, so they can move freely.

All can be softened & made more mobile with massage. You'll need it a little deep, to work on whatever the problem mite be. But same type of massage would work for knot, scar tissue, or adhesion.

If it's really bad - mebbe ultrasound by a PT...?

Good luck.