From https://www.irs.gov/publications/p525#en_US_2021_publink1000229331

Workers' Compensation

Amounts you receive as workers' compensation for an occupational sickness or injury are fully exempt from tax if they're paid under a workers' compensation act or a statute in the nature of a workers' compensation act. The exemption also applies to your survivors. The exemption, however, doesn't apply to retirement plan benefits you receive based on your age, length of service, or prior contributions to the plan, even if you retired because of an occupational sickness or injury.