Suggest Treatment For Sternum Pain

I've had a pain in my sternum for a few months now. If I turn or twist, tighten the muscles in my chest there is a dull pain in my sternum - as though somebody is pushing a finger into it. I notice it most if I raise my arm, shoulder level out to my side and then put my head back (so I'm looking up) .. Sometimes I can nip the skin in the area and feel a pain between my fingers .. Any ideas?