If it had a white pus in it, it probably wasn't herpes.
A blood test is useless for this purpose. A blood test tells you what you have, not where you have it. Even though your first blood test was negative, even the best herpes blood tests still miss 1 out of every 10 hsv1 infections so if it's positive now or in a few months, no way to know if you have hsv1 orally or genitally or if it you had it all along or if you contracted it from this partner. The best course of action would be, should you get a return of symptoms, see your provider within 48 hours and get it properly evaluated and if they feel it's herpes related they can culture it for you.
You really are way over reacting to this as Jess already said. The odds that you contracted hsv1 from your partner are incredibly low. It's really not worth allthis time and worry you've put into it. Pimples and ingrown hairs are normal and happen to everyone. Not everything in the genital area has to be due to herpes.
grace
OK, sorry for beating this into the ground. There is obviously something wrong with me, as I still think this pimple may be a herpes blister. I'm thinking the only way to ease my mind is to have a blood test performed (I popped the pimple, which excreted a white puss, 3 days ago, and the pimple is almost gone, so I doubt that it could be cultured). If this is a herpes blister, will the blood test come back positive for HSV, or should I wait a few more weeks so that antibodies can develop?
One other question: I've read online that heterosexual males usually develop herpes blisters on the penis, not near the anus (the online source cited the CDC, but I didn't check this reference). I guess this is the typical pattern, but there are exceptions, yes? Sorry for the multiple posts; this is my last one, promise.
Yes, you could, but blisters can also be hemorrhoids, so you need to get that checked before assuming anything.
Aj
Thanks, I think you're right (definitely over-reacting). Just curious: Could you develop blisters near your anus from vaginal sex with an HSV positive woman?
I think you are overreacting. Genital hsv1 rarely sheds - about 3% of days a year, and she is on valtrex.
The chances of you ever getting ghsv1 from her are so slim that she probably doesn't even need to take the valtrex.
This could be a pimple, a cyst, staph, etc. If it doesn't get better in a few days, then see your doctor, but its not herpes.
You should read this - http://blogs.webmd.com/genital-herpes-intimate-conversations/2006/02/type-i-herpes-transmission.html