Crack in the fretboard or what?

Hello, so I won(?) an auction and had this soprano mahagony ukulele some week back. But, when I take the strings off I find there´s a "line" or mark, that runs parallell to the F# string in the fretboard. My first thought was that it is something that appeared from the making of the instrument. Then is struck me that it might be a crack, how can I please find out if this is a crack or just a scar?
When I run the tip of my nail over it I certainly feel it. It goes all over the fretboard.

Regards

Looks like a mostly normal fissure in the wood, along the grain line. Maybe a bit more pronounced that most. If you don't feel it when you play, it should be no problem.

Thanks for your reply. How would you say these fissures arise?
How to tell if there is a normal fissure or a crack in the Wood, please?
I can see two hair lines, parallel from the nut to approximately the 8th fret. There after just one hairline to the 12th fret.
Regards

It's simply an exaggerated grain line. If you can't feel it, no worries. It's all securely glued down and won't go anywhere.