Cracked toilet?

While cleaning the floor in the bathroom, I noticed that my toilet has what looks like to be a hairline crack in the bowl coming from around the floor bolt cap straight up the side of the bowl. The hairline crack is probably less than two inches in length. I run my fingernails across it and I cannot feel any break in the finish of the toilet. It looks like someone penciled a line on the side of the toilet. Is this an internal crack that is slowly making it's way to the exterior of the bowl?

Is this anything I should be worried about? The toilet flushes fine and does not leak. The toilet is about 15 years old.

Thank you for any advice!

An over-tightened toilet bolt could have started the crack in the base. If it gets larger and starts leaking, you'll have to replace the toilet.
Mike

crack

Without removing the bowl to check inside to see if the crack goes all the way through and how long it is, there is no way to determine if it has any serious consequences.