How do I pursue a civil lawsuit from receiving a personal injury at an MMA gym and not signing a waiver?

I received an injury from a local MMA gym and was never made to sign a waiver. However the coach was very happy to receive my money for the class. He paired me with a partner be was originally training with who is three times my size and I got an injury. He even pushed me to train on my injury after fit took place. He got me to train with him by recommending to the person I was training tk stop and put his cup on and instead of waiting for him to return he sent me to train with the other guy and didn't tell me to put on shin guards and I was unaware we had shin guards for the public use