Your employer, or typically their insurance company, is responsible.
Your employer has to pay your workers' compensation benefits. They're either individually responsible, or, most employers secure workers' compensation insurance that in turn is sometimes, and perhaps typically, overseen by a third party administrator. But certainly, your employer is responsible -through insurance or otherwise- for providing wage loss benefits and medical benefits. Now, the workers' compensation law is supposed to be self executing. These benefits are supposed to be delivered to the injured worker without any prompting or any legal action. But the fact that we have a workers' compensation litigation system and workers' compensation commissioners that hear these claims suggests that -obviously- it is not a self executing system and sometimes litigation is required to secure these benefits.