Hello
Thanks for posting your query at DoctorSpring.com
I can understand your concern.
It seems to be nail fungus . It's caused by a fungus called dermatophyte. It causes this kind of nail change.
The treatment for your toe nail fungus or onychomycosis would be oral terbinafine for 3 to 6 months.
It doesn't look like a melanoma. However, it would be best to consult a doctor who can just examine the nail once, and make sure about that.
Please let me know if you have any queries.
Regards.