I have two vertical black lines on the side of my left thumb fingernail also i have another one on my right thumbnail i didn't smash either nails?

get eva;: Black stripes down one nail could be a subungual hematoma. Red or brown streaks could be splinter hemorrhages. Brown/black lines from the nail plate to tip are often seen in people with dark skin & are normal. Subungual Melanoma can cause nail ridges and dark colors of the cuticle. It usually begin in the nail matrix. It most often effects the thumbs or big toes. Get checked out when in doubt.