There is no easy way to analyze this without more data. You need the specific name of the condition. See, whether a medical provider is at fault always boils down to whether the standard of care was violated by failing to more timely diagnose the condition. Every medical condition is...different. Different symptoms, different methods of diagnosing it, etc. For example, they may have fault for failing to order an x-ray after the patient presented on several occasions with a bad cough that was not helped with common meds...and then 3 years later was diagnosed with Stage IV lung cancer.
The discovery rule typically applies only when there is no prior knowledge of the linkage of any kind between the wrong act and ANY damage. If it is known that there was a wrong act and some damage suffered, the fact that new damage is learned does not typically implicate the rule. I would not think that it applies.
Did you bring lawsuits for the auto accidents? Have they been settled? If not, maybe you can claim the exacerbation of the injury was from one or both accidents. You have not given enough facts to determine if you have a statute of limitations problem on a medical malpractice claim or even if the failure to diagnose the condition in a more timely manner was malpractice in the first place. Consult a local medical malpractice attorney immediately.
I assume you are an attorney, which is unusual for this forum. However, I'm in Cherry Hill and would be happy to discuss with you in more detail.
Please note that these answers are provided as a community service and are not meant to create an attorney-client relationship.