I had a very sore big toe. iys fine one day the next so sore could not touch it. the nail turned dark purplr or black . i knew that it had blood under it. so i released the blood. now pain has eased. but im going to loose the nail again because it happened before. 2014. just out of the blue it starts hurting then turnes black and hurts like crasy. i also have high sugar what is the cause.