My thumb I think it was got cut by a window...and the cut was deep but i tried to ignore it. Until it started turning black and was about to fall off! Like in frostbite...so i went to doctor and saved it.
Maybe this is going to sound too obvious, but the dream could suggest that you have been hurt, perhaps emotionally, and you have "tried to ignore it". But ignoring it is not working and so you know you must do what you must to heal this.