I have small black lines on my one fingernail. should i see a doctor?

Splinter Hemorrhage: A splinter hemorrhage can occur for a variety of reasons and may be harmless or a sign of a more serious health condition. If caused by trauma these usually resolve after a few weeks. If no resolution or if accompanied by other symptoms such as fever, pale skin, joint pain, shortness of breath, a more serious cause needs to be considered and a doctor should be seen as soon as possible.