Did I lose my rights to a doctor by signing that release after I was hurt on the job?

During working hours, I slipped on some ice. I hurt my knee reported and it to my boss. He filled out the paper work and asked me if needed to see a doctor. I said I'm not sure. He said well most the time and as swelled up as your knee, they will have you ice it then come see them in a few days. I said that sounds fine. He then handed me an “I don't need to see” a doctor form. But he said you can go see the doctor if it gets worse and to just wait and see. I shined it. I got fired the next day for none productivity. I only was on this job a month and was getting training for three weeks. I had two days before this the accident happened of just getting my user name and password. I could do work until I got that. So none productivity was BS. I got let go for falling down. It's been two days now since they fired me. Now my back is hurt. My knee had gone down but I still can't walk very well. They won't call me back.