Typically when you settle a case you enter into a general release ending all claims arising out of an incident.
Whether you could proceed with a second action would depend on the terms of the release in the first action
and it expressly permitting you to proceed with another claim. This is not usually done.
The statute of limitations for a medical malpractice lawsuit will vary state by state. Without knowing in which state the medical malpractice occurred, it is impossible to know what the governing statute of limitations will be.
Also, please know that lawyers are licensed by individual states. Therefore, you will want the answer to your question to come from a lawyer that is licensed in the state in which the medical malpractice act occurred.