I have a red bump on my arm that started out like a little blister then got bigger probably the size of the end of a pencil eraseer. It has an opening in the middle it does not itch and doesnt hurt. I went to the dr and she said it was a skin virus and named a long name off but i cant remember what she call it. Also stated it could last months to a year and nothing needs to be done to treat it but a cream could be used to help it go down.