laid off because I was hurt and asked supervisor to contact workers comp

I had a job where I I had to reach 6' to get meds from shelves. She knew it was hurting my shoulder but would not move the shelves to a lower position. My shoulder kept getting worse over time. I finally insisted she call workers comp but she refused. I asked her at least 4 times next thing I knew i was laid off. I had more senority over the others. She said it was because they were certified and I wasn't . The State of Tn doesn't require certification. After I was laid off they changed them to certified tech and back paid them 3 years.