I really think it was some type of bite. I have had no other unexplained bruises. It happened the day I went hiking and got stung by a honey bee. the bee sting was on my right finger and the bruise/bump was on my left arm. The bruise went away but it took the bump much much longer to go away. there was a slight possibility that when I got stung by the bee I might have bumped something and not felt it do to the pain of the sting. I had no other reaction to bee sting except for pain--minute swelling which left soon.
However this does not explain the bump and appearance of a small hole in it.
I guess it is one of those mysteries. I will pay you for your time but feel it didn't answer my question--perhaps there is no answer to this question.
Thanks
Jeanne Prather-Laird