what legal action can I take?

I recently got injured while at work asked if I could go to the hospital an was refused I finished out my shift an went after work on my own time to find out I have a strained muscle in my right shoulder possible tear in it I have to call a specialist to make sure its not damaged bad. I went to work the following day gave them the doctor note an was told I had to resign due to I could no longer do my job function what can I do legally due to the fact the company would not help me even tho I got injured at work while on clock