Urgent help needed really sore back and shoulder any advice?

Well long story short I hurt my back on fiday last week playing basketball, a large guy landed on my back as I was about to shoot and I snapped my neck backand felt lots of poping and heard cracking, carried on running for a bit longer but a minute later sat down, my back automatically get lots of pain in it. I still have a sore back on tuesday (thats today) but have developed a sore shoulder and it feels like muscle pain but its burning and evertime I move my arm sharply or really at all I get a realy sharp pain, Its getting me quite worried Its like rights on the bottom of my arm, at the back where your armand back meets anyone know what this could be? thankyou I'm 17 year old female quite tall