Being that u have cold sores all your life, I'm not sure if it can detect that. You would have to ask your doctor about that. But I know for sure that if u get any tingling or discomfort on your genital area then a blood test is the best way to find out if u have hsv-1 or hsv-2.
How would a blood test detect anything? I had cold sores all my life. Wouldn't the blood test just show that I'm postive for Herpes simplex 1?
I doubt that she could've gave you the cold sores on your penis if it was completely healed then ders no reason to worry. But if you start havin tingling or pain den I advise you to take a blood test. Just to be safe.