What does trauma to a toenail look like?
If you stub your toe or drop something heavy on your foot, you may develop a subungual hematoma , which is blood and fluid trapped beneath the toenail. This gives the toenail a red, black, or purple discoloration.
Why is there a line in my big toenail?
More than one line on one of your nails is usually a sign of repeated external injury to the nail matrix or an infection. However, if you have more than one nail with Beau’s lines, the cause is likely a systemic illness, prolonged exposure to certain environmental factors, or chronic disease.
Is caused by physical trauma or injury to the nail bed that damages the capillaries and allows small amounts of blood flow?

Splinter hemorrhages are caused by physical trauma or injury to the nail bed that damages the capillaries and allows small amounts of blood flow.
What does melanoma look like under the toenail?
You have a brown-black colored band on your nail that is larger than three millimeters in size with irregularly shaped edges. The discoloration grows, and at what rate it does so. It’s in the nail bed of your thumb, big toe, or index finger, although it can be seen in other fingers and toes.
What does a black vertical line on toenail mean?

A narrow black line that has formed vertically underneath your nail is called a splinter hemorrhage. It occurs for a variety of reasons and may be harmless or a sign of a more serious health condition. This condition is called a splinter hemorrhage because it may look like a wood splinter under your nail.
What causes a black line on toenail?
Melanonychia is caused when the pigment cells, called melanocytes, deposit melanin — brown-colored pigment — into the nail. These deposits are usually grouped together. As your nail grows, it causes the stripe of brown or black to appear on your nail.
What is Beau’s lines of the nail?
Beau’s lines are indentations that run across the nails. The indentations can appear when growth at the area under the cuticle is interrupted by injury or severe illness.
Why is there a black line in my nail?
This condition is called a splinter hemorrhage because it may look like a wood splinter under your nail. The condition is caused by damaged small blood vessels underneath your nail.
Will black line on nail go away?
Splinter hemorrhages appear as small black or deep-red lines and are caused by injuries to the small blood vessels under the nail beds. They usually heal on their own within a few days.