The lesion you describe does not sound particularly like herpes, both from the location and from the description itself; it sound more like folliculitis or an infected cyst. If you have not been exposed to another possibly infected person in the past year, you know for sure you are not infected; i.e., your blood test results prove that your abdominal lesion could not have been herpes.
Put herpes out of your mind; you don't have it. If you get other skin lesions you are concerned about, see a provider right away. (If your own doc isn't available, you can always visit an urgent care clinic, planned parenthood, etc).
Good luck-- HHH, MD
That does not sound like herpes, especially if it pussed and popped. It sounds more like an infected hair follicle or pimple. If it's right wear your pants are it could just be a blister or blood blister from the friction of your pants against your skin.