What proves the accident was not in any way my fault?
There must be strong evidence that the location where the accident occurred was not cared for as well as possible by the person in charge of it. It must be evident there was a hazard that could have been remedied, but you were forced to work in the area without the necessary precautions. If there’s an indication the person in charge of the operation didn’t keep dangerous obstacles out of the area, clearly they’re at fault.

Do I have to fill out a report right after getting into the accident?
Not technically, but if you can, you should. Fill out a report as soon as possible, that way you can recover as steadily without worry. Mention every critical detail you can remember, such as witnesses, lighting, surface texture, etc. Also try to take photos of the area, so your attorney can see the scene through your eyes and use that insight to support their arguments.

How long after the accident can I file suit?
Your time limit, the official legal term for which is, “statute of limitations”, depends on which state of the country you’re in and whether any personal belongings have also been damaged. If there’s any property damage on top of your bodily injury, there’s more time allotted in some states, and less in others.