I suddenly noticed a painful reddish area on my hand 3 days before in an evening. As shown in attached picture, these 2 bite like marks are exactly on my elbow and there is 2 bites on both sides. And only the reddish area is bit painful. The inside area is not that sensitive, but showing slightly blackish after today morning. Can this be something to be worried about. I have absolutely no idea what bit me or is it something else. Please advise.