Maybe irritation from the hair? I had cuts like that on my vagina years ago and was negative for hsv 1 or 2.
It could be, or it could be something else. It's hard to say. The buttocks isn't the most common place for an outbreak, but everyone is different. Can you think of anything that might have caused an open sore there?
If you have antivirals, you should take them, just in case. It won't harm you if it isn't an outbreak.