Should I be concerned about my mole? Turned into a blood blister. (Photo)

I had a small brown mole on my leg since birth, last October it changed to a what looked likely a dark blood blister with a red ring round it (picture 1), after about 4 weeks it turned skin coloured (picture 2) but slightly raised and has been like that until a week ago. It has now started to turn into a blood blister again (picture 3)