Upper Back Injury!

I think I have an upper back injury. Thursday at work we did about 130% of a good days work, and throughout the day I felt like I had a peice of bone/tissue sticking out of my t-shirt.

When I dont touch it, I would describe it as being the horn of an anvil. I am guessing probably 3 inches below my rear delt. It started hurting friday, but not real bad. When I touch it, it feel like it is the size of a protein powder scoop, but it is not terribly visible in the mirror.

I still feel like I have all strength and mobility. What is it, and how can I fix it?