An oral report is certainly better than not reporting it at all, but the supervisor can deny you told them anything later. A written report is best, and removes all doubt that you reported your injury. Your company may have a form for you to complete, or you can just handwrite a letter to your supervisor to let them know what happened. Make sure to keep a copy for yourself and give the letter to any and all supervisors that need to know that you were injured on the job.
Seek Medical Attention
I recommend that my clients see a doctor immediately, even if they aren't sure they need to. My rationale for this is that if you are injured on the job, and you wait to see a doctor, than the insurance company can use the fact that you waited as a way to deny your claim. If you see the doctor immediately, then the accident will be fresh in your mind and you can give an accurate and detailed description to the doctor of what happened and how you are feeling as a result.
Talk to a Workers Compensation Attorney
Most attorneys, (myself included), that handle these types of claims work on a contingency fee. This means that we won't charge a fee unless and until we recover financial compensation for you. It is entirely possible that you will not immediately need an attorney to help you with your case, and many cases proceed through the Industrial Commission with no attorney involvement. However, it will not cost you anything to speak with an attorney, so why not take advantage of that resource? A Workers Compensation Lawyer can talk to you about preserving evidence, taking photographs (if necessary), and the need to get experts or other witnesses involved early on. Most workers are more concerned about getting medical attention (rightly so) than they are about preparing their workers comp claim.
File your claim properly
In order to get your case opened up at the Industrial Commission in Raleigh, you must initial your claim by filing a Form 18. Don't rely on your employer to do this.
Cooperate (carefully) with the Insurance Adjuster
Soon after you have submitted your claim that you were injured at work, you will be getting a call from an insurance adjuster whose job is to determine whether or not you were injured on the job in an accident. If there was no accident, than the insurance company will deny your claim. You must be very careful when you talk to the adjuster -- if you are on medication or feel confused about the questions you are being asked, then ask them to give you a few days until you feel better and have a clear head. Make sure that you have your notes ready that can give the adjuster specific facts about what happened, when, and whether there were any other witnesses to what happened. Do not discuss personal matters with the adjuster. They will be very nice to you -- that is how they get you to open up to them so that they can find a reason to deny your claim. Be cooperative, but be careful as well.
Keep records of your correspondence
Each time you talk to the adjuster, they are making a record of the contact and what was discussed. You should be doing the same. Make sure that you get a notebook and keep a record of the date, time, and name of anyone you talk to from the insurance company, as well as a note about what was discussed. This information will be invaluable later on, especially if your case has to go to a hearing.
Follow Doctors Orders
Make sure you fully understand the instructions given to you by your doctor and follow them closely. If you are given a weight restriction, you should assume that someone from the insurance company is following you around with a camera to try and find you violating that restriction. If you are injured on the job and then return to work with restrictions, don't be a hero and try to do more than you are allowed to do -- this is a sure fire way to blow up you claim. Make sure you get to your appointments on time and be presentable. If for some reason you can't make an appointment, make sure to call ahead in plenty of time to reschedule. The last thing you need in your chart is an unexplained "DNS" (i.e. Did Not Show) that helps to prove your unwillingness to cooperate. If you feel that your physician is uncooperative or otherwise not listening to your concerns, you may always file a request with the Industrial Commission to have your case transferred to another care provider.