OK! I'm back with more information:
In my dad's case it was Lichen Sclerosus. His dermatologist (the best I've ever met) told him it's often misdiagnosed as a simple abscess. It starts with an itchy area, but can get infected and develop into sores. He had it on the exact same place as you have it, but it wouldn't go away with abx and got bad, so they had to clean it out surgically, but it healed very nice and rather quick.
She told him it often flares up when immunity is low, or with high emotional stress. Gotten it once, it can come back easily in the 'right' circumstances. She told him that it forms at the end of a damaged nerve.
I just had a very quick look on the internet, and stumbled right away upon this: http://www.bbc.co.uk/health/physical_health/conditions/lichensclerosus1.shtml
and look what's written in this article:
In recent years there has been renewed interest in a possible link with a group of micro-organisms called Borrelia, with antibodies to this bacteria found in more than a quarter of cases.
Once the sore is cured, and you experience an itchy feeling, she adviced to dry the area with a hair dryer after showering or bathing, and apply a cream to keep the skin 'elastic' so it won't itch or crack (and afterwards get infected).
Just a thought, I'm not a doctor