Where was the lidocaine injected? Do you know how much?
What the injection for?
Can I ask the reason for the question?
Absorption of lidocaine depends on site of injection, and half life is also variable as the lidocaine is extensively metabolized quite quickly but the metabolites will have a longer half life.
If you were to assume that all lidocaine was out of the body in a couple of days,and the active metabolites perhaps a few days longer that would be a good approximation. Things that affect this include body weight and water content, as well as renal and liver function.