When you can claim
The first thing to realise is that if ever you are injured in an accident that was not your fault then you are almost definitely entitled to compensation. That however is an almost definitely not a definite definitely.
The reason why this is so is because most accidents do not happen by accident, as it were. Usually it is somebody's fault and therefore if it is not your fault it must be somebody else's fault. If it is somebody else's fault then you can claim compensation from them, or more realistically in the vast majority of cases from their insurance company. If you are unfortunate enough to be injured in one of those very rare accidents that just happens accidentally without anybody being to blame, then you're not entitled to any compensation.
This is because the legal entitlement to compensation arises in most cases from the fact that somebody was at fault, not simply from the fact that you have been injured in itself.