Dark toenails

Patient: I am 25 female type 1 diabetic since I was 13 my substance are generally ok. For the past seven years both big toenails are almost black. There is no pain but the nail is extremly thick. I know I should have showed my doctor but I am Sooo emmbarrassed will I have to get this amputated ? What is it el or can it ever go away I cannot even wear sandals in the summer time.. please help