On my middle finger, appeared a month ago. Total length about 5 mm.
If you have had this a month and it hasnt faded then you should get it checked out as soon as possible. Impossible to tell on here exactly what it is but better to be safe than sorry.
Asymmetry: The mole has an irregular shape. Border: The edge is not smooth, but irregular or notched. Color: The mole has uneven shading or dark spots. Diameter: The spot is larger than the size of a pencil eraser.