If it is an emergency, get medical attention immediately. If it is not an emergency and you are able, tell someone from your job (preferably your supervisor) that you got hurt. In the cases of occupational injuries which develop over time and not in one specific incident, that might not be feasible because you will not know the exact moment in time that you got hurt. Instead, as soon as you know that you have an injury, tell your employer. Notice to your employer can be crucial in workers' compensation cases.
Next seek medical attention. Even more crucial than giving notice to your employer, is giving an accurate history to the medical provider that you treat with. Make absolutely sure that you tell them how you got hurt, that it happened at work and what body parts are injured. In most cases a Judge will look at the first medical record to see what the employee says happened and what they hurt.
After that, it is highly advisable to contact an attorney who is experienced in workers' compensation law who can guide you through the process. Most people are at a distinct disadvantage when it comes to dealing with the insurance company and their representatives due to their lack of knowledge of the law and the system. Hiring an attorney can help you level the playing field and make sure that you are protected.