Keep it, and do not repair, alter, clean, or throw it away. The product itself is almost always the single most important piece of evidence in a product liability case, because proving the defect usually depends on an expert examining the actual item that failed.
Preserve everything that came with it too: the packaging, labels, warnings, instruction manuals, and your receipt or proof of purchase, along with any model and serial numbers. Photograph the product and the scene of the injury, and write down what happened while it is fresh.
This matters because manufacturers routinely argue that a product was not defective, that it was misused, or that ordinary wear caused the failure. A preserved product allows an independent expert to test those claims — and losing or discarding the product can seriously weaken, or even end, an otherwise strong case.