Sternum injury?

(mind you first that i went to a doctor and they said the y aw nothing wrong, and did no x-ray.) I got elbowed in the chest a couple weeks ago and since then i have had a pain the my sternum that increases with stretching back, raising my arms, propping myself up on my elbows and make s a loud snap click when i lean back then forwards again. in addition to this the pain has spread to my upper left ribcage into my clavicle, shoulder and upper back. today i started feeling the pain on the left side of my neck and the right side of my clavicle. it hurts when i breathe in and when i cough or sneeze. what could this be?