Hire a Workers Comp lawyer.
Most states have anti-discrimination laws for employers taking retaliatory action (which can sometimes include other acts besides termination, including demotion, or other discriminatory actions, like probably taking away previously granted vacation time) after an employee reports a work-related injury.
Here's something from a website, specifically referencing retaliatory terminations in Idaho, but probably should hire a lawyer in your jurisdiction who specializes in Workers Comp and/or Labor law:
"There is authority in Idaho under which a common law wrongful termination claim for workers’ compensation retaliation may be premised. Pursuant to the common law public policy exception to the at-will employment doctrine, discharging an employee for filing a worker's compensation claim constitutes wrongful termination. See Jackson v. Minidoka Irrigation Dist., 563 P.2d 54, 58 (ID 1977) (listing cases illustrating the public-policy exception to the employment-at-will doctrine, including Frampton v. Central Indiana Gas Co., 297 N.E.2d 425 (Ind. 1973), in which the plaintiff was fired for reporting an injury to her arm so she could file for workmen's compensation, which the Indiana court held to be in clear contravention of public policy); see also Thomas v. Med. Ctr. Physicians, P.A., 61 P.3d 557, 565 (ID 2002) ("This Court has also indicated that the public policy exception would be applicable if an employee were discharged, for example for refusing to date her supervisor, for filing a worker's compensation claim, or for serving on jury duty.") (citing Sorensen, 118 Idaho at 668, 799 P.2d at 72); Prado v. Potlatch Corp., 2006 U.S. Dist. LEXIS 68874, 12-14 (D. Idaho Sept. 7, 2006)
An employee may claim damages for wrongful discharge when the motivation for the firing contravenes public policy and the employee bears the burden of proof to show that the firing contravenes public policy. See Jackson v. Minidoka Irrigation Dist., 98 Idaho 330, 333, 563 P.2d 54, 57 (1977)."