Accident at work - triped on cardboard box

hello
last week i had an accident at work. I'm working in shop with office things (like paper, chairs, etc.).
Yesterday someone leave cardboard box on the floor. While going back from magazine to store, I tripped on this carboard box and fell on my knees. Both of them are broken now. I stayed in hospital for 5 days, had 3 operation
When I asked my employer if I could get any compensation, he said: "Do you want to work here still or you consider to leave us?" So I don't know what to do What I know is that my accident will cost me a lot (operation costs few thousands of pounds, my doctor said). Do I have a right to claim my work colleague? Or employer, but I'm araid to lose ths work:/