I have black lines on my toenail is it something i should be worried?

Black lines: This could be caused by your skin color with melanin within the nail root. If there is one line or so and your light skinned i would have it looked at.

Could be melanoma: Said, not to scare you, but to get you to see a dermatologist or podiatrist. Sometimes dark lines can be a sign of malignant melanoma. Sometimes not. Could be as simple as bruising or splinter hemorrhage. Even splinter hemorrhage can be sign of other systemic issues. Your doctor may want to do a biopsy to make sure.

Black lines: Could be serious or not. Possible melanoma and play if save than sorry. See dermatologist or podiatrist where a small biopsy may be performed.

Just get checked.: Black stripes down 1 nail may be subungual hematoma. Red or brown streaks may be splinter hemorrhages. Brown/black lines from nail plate to tip are often seen in people with dark skin & are normal. Subungual Melanoma can cause nail ridges & dark colors of cuticle. It most often effects the thumbs or big toes. Dark lines may be due to other illnesses. Get checked out when in doubt.