Because they were paying you in cash, it is unlikely they were providing worker's compensation for  you. Without worker's comp, your only option would be to sue your employer for the cost of your medical care (the portion she has not already paid). To win, you'd have to prove in court  that your emplohyer was responsible in some way for your injury, such as by defective tools, defective procedures, etc. If your employer were not responsible for the injury, they would not be liable for your medical costs--liability depends on fault.