Hi, I am in my 30's and live in UK. I have a long existing (5 years or more) infected thumb nail on my right hand. Both sides of my thumb nail have vertical black areas with a mass (5 mm Diameter) at right corner of nail bed. The left corner also looks like having a mass of 3 mm but isn't swollen much and is unnoticeable. The right mass is dark brownish and has a swollen appearance and doesn't hurt on its own but when I wash dishes some day, the swelling goes red exposing slightly the inside layer of nail bed and hurts. Sometimes the right mass is also itchy but I avoid the urge. 

I tried getting treatments for it in my home country and Dermatologist suggested anti-fungal course for a month and nothing happened. The infection is still there. I didn't go back to the doctor for 2nd consult. I was going through nail cancer articles and I am scared now, what if my nail condition is cancer and I have delayed screening thinking it's fungal. 

Can someone tell me what other symptoms one might observe physically if they got periungual/subungual melanoma ? Would there be any dizziness, vomiting, chest congestion or any other physical discomfort that are tell tale signs of ungual melanoma spreading to other parts of body ? I contacted GP for a fungal infection and she asked to provide nail clippings. Will they test the clippings for cancer as well or I need to book another appointment to get cancer screening of the nail and mass ? 

Wish I could upload a picture for better clarity.