A few days ago I shared a bed, but did not engage in any kind of sexual act, with a girl.

Today I noticed a dark red mark on my penis. It is fairly near the top on the underside, it is not swollen or raised above the skin. The mark resembles a bruise or an abrasion and is purpley pink in colour, smooth and about four or five mm in diamter. I haven't really noticed any obvious kind of sensation in that area e.G. An itch, other than ones maybe caused by paranoia.

I was just wondering if this could be a bruise or something more sinister? I'm extremely paranoid and ocd about this type of thing. It couldn't be a sympton of herpes for example could it?

Thanks.