I'm 16 years old and i have brown under my nail(foot, not big toe).its covering almost half of it. i barely noticed it today. should i be worried?

Remember Bob Marley.: Reggae music star Bob Marley had a similar "black spot" under his toenail, that proved to be a malignant melanoma ultimately leading to his demise. While melanoma is not commonplace in your age group--it does and can happen; since you are uncertain as to what this lesion is precisely, you should consult with your family doctor or dermatologist for a better answer.