Can you upload a picture of your nail?
You can post a link to flickr or use the tree icon on the toolbar.
Try and get a real good close up if you can.
Your line is regular and of uniform color - so a benign malanocytic nevus is the most likely diagnosis.
Melanoma - are irregular in shape and color.
For sure you need to let your own MD have a look but from the images that you have posted I would consider a "serious" problem most unlikely.
YOU ARE VERY WELCOME!!!