Is this something serious?

https://imgur.com/a/pDJCHNX

I just noticed this vertical darkish line that runs from the tip of my left thumbnail to the back. It doesn’t seem to be there last week. I’m not sure if it could be something serious.

Here’s some information about myself:

Age - 24

Height - 177cm

Weight - 73kg

Gender - Male

Meds - Methimazole for hyperthyroidism

Non-smoker

Medical issues - hyperthyroidism (under control)