I have Harrington Rods in my back. I informed my employer that I could not hand unload my semi trailer which has to be done very seldom. They were in a bind and sent me on a hand unload anyway. I injured my back again and am on work comp until it heals, at least another month.
I don't understand your question. If you were hurt at work, Workers' Compensation is your sole remedy. Presumably, you are receiving weekly benefits and your medical is being paid. If benefits are denied, consult a Workers' Compensation attorney. You state no facts consistent with a discrimination claim. You had every right to refuse the assignment if it exceeded your restrictions. You foolishly accepted it to your detriment.
The ADA becomes relevant when an employer performs an action adverse to your employment (e.g. fires you, reduces pay, reduces hours) because of a disability or condition. Based on the limited info here it doesn't sound like you were discriminated against in an ADA context by being asked to do a task that injuered you. I hope that answers your question.
If you are off of work because of the work injury then you should receive wage reimbursement after the 8th day that you are unable to work. If those benefits do not arrive by the 15th day after the injury you should contact your employer to confirm that a work injury claim has been filed for you. If that fails you should contact a lawyer. Best of luck.