Black vertical lines under fingernails
I recently started to develop vertical black lines, quite thin and short, running down my nails. There are multiple black lines next to each other on more then 4 fingers. I noticed that both my hands have the black lines on the same spots as each other, which is odd. the only fingers i dont have anything on is the thumb and index finger.(pinkys got one 2 days ago, right in the middle of the nail, same spot on both pinkys...although the one on the right hand is a bit fainter, but its coming) if it helps i used to severely bite my nails, pretty much my entire life. but i quit doing that about 2-3 months ago because of a injury at work to one of my fingers, which had led to a deformed nail on the right index finger, the nail and part of the nail plate got torn of that one and has been healing ever since surgery. Anyways, Im only 20, and from what ive read it can be a sign of heart problems, but our family doesnt have history of it from what i know. if it helps i could take a picture. Any help would be appreciated. Thanks!