What is this thing?

By definition it's an ulcer if it doesn't heal promptly, but that doesn't tell you the cause. Don't rub it with alcohol. You'd need to talk to a doctor to understand the etiology of it. Otherwise just clean it with sterile saline from the drug store and replace it's dressing(in this case a band aid) periodically. A small amount of soap and warm tap water is also sufficient generally for anything superficial (but not antibacterial soap as that will delay healing similar to alcohol). If it becomes infected, you need an antibiotic. If you don't figure out the cause from taking to a provider it could become bigger and worse. This is particularly true if you're diabetic, have venous insufficiency, or peripheral artery disease. Overall though, it looks good, with plenty of good pink tissue and no eschar or signs of inflammation.