That's funny, quarantine sex with the girlfriend like it is different than regular sex. I like it, we are living in crazy times, aren't we? Anyway, Our penises are sensitive skin. You got an abrasion. I take it this is a monogamous relationship? This wound happened during the event? Then that is the cause, right? Well, it appears so from what you are telling us anyway. https://www.healthline.com/health/cut-on-penis#causes This lists sex as a cause of friction injuries. There are other things that cause penis cuts/abrasions but your situation sounds fairly straight forward. Petroleum jelly often helps.