Please try not to worry. I had the exact same dark line appear on my big toe nail. I've had a melanoma removed from my leg before, and was petrified. I was initially tested for a fungal infection, but nothing cleared it after a year of treatment. The line was then monitored for a further 6 months by a dermatologist and, albeit slowly, looked to be getting darker and wider so my whole toenail was eventually removed and a biopsy taken.

It turned out to be nothing, just a discolouration that could have been down to a slight fungal infection.

This is so reassuring. The waiting is awful. I'm in the same situation as you today. I had a stage 1a melanoma last year on my back. I've had a dodgy toenail for a long time. Treated it for fungal infection had it tested twice and nothing has come back. Had black patches in the past which have gone, however at the start of February I developed a black streak. Been to the consultant today and he's removing it for biopsy on the two week wait. I'm petrified. 

This is so reassuring. The waiting is awful. I'm in the same situation as you today. I had a stage 1a melanoma last year on my back. I've had a dodgy toenail for a long time. Treated it for fungal infection had it tested twice and nothing has come back. Had black patches in the past which have gone, however at the start of February I developed a black streak. Been to the consultant today and he's removing it for biopsy on the two week wait. I'm petrified. 

Please try to stay calm, and stay off google if you can. I drove myself absolutely insane and was convinced myself it was the worst possible scenario. 
 

Recently my partner was put through the two week wait for bowel cancer. I did the exact same thing and googled and got myself into an awful state thinking the worst. That again turned out to be something very mundane and treatable. 
 

So just take take each day as it comes. No amount of worrying will change the outcome and the NHS is incredible and will provide the best possible care whatever the outcome xx