In most states, it is a violation of the workers' compensation laws to retaliate against an employee for filing a workers' compensation claim. If this happens, immediately report it to your local workers' compensation office.
While the federal government administers a workers' comp program for federal and certain other types of employees, each state has its own laws and programs for workers' compensation. For up-to-date information on workers' comp in your state, contact your state's workers' compensation office. (You can find links to the appropriate office in your state on the State Workers' Compensation Officials page of the U.S. Department of Labor's website.)
In general, an employee with a work-related illness or injury can get workers' compensation benefits regardless of who was at fault -- the employee, the employer, a coworker, a customer, or some other third party. In exchange for these guaranteed benefits, employees usually do not have the right to sue the employer in court for damages for those injuries.