Most newly infected people have positive tests within 9 weeks. Combining the low risk of the exposure, your lack of herpes symptoms, plus the negative blood test results, you can indeed be 100% certain you did not catch HSV-1. I suggest you stop testing, or at least follow the advice of a health professional about it.
I saw this comment before I replied above. It does not change my opinion or advice. Your frequent masturbation probably has nothing to do with the skin lesion.