A sudden onset of pain and bony bulge felt at back, below neck, at level t1, between shoulder blades, with pain radiating towards chest. what is dx?

The sudden onset: of your pain, combined with the fact that you describe it as a hard, bony-like bulge makes this diagnosis more challenging. Collection of adipose/fatty tissue in this region is not uncommon, but that would be neither suddenly painful nor "bony." A bone spur can develop in this location, but no sudden pain. Trauma? not typical. Needs in person evaluation with Doc/Spine specialist. Good wishes:)