They're small cracks and it sounds like they've been there for years without growing. Personally, I wouldn't worry about them, just check on them every year or so to see if they change and to keep weeds from getting a foothold in them.
Cosmetically, you could force some concrete colored caulk into them.

Now you know about them, where they are.

If your home, otherwise, is performing satisfactorily, just leave them be.

But keep an eye on them, give them the old once over each spring, say. If they start to move or open up...well there are lots of things to explore at that point. Doesn't sound like you are at that point at all.

If you are in an area that has freezing weather and snow you should at least close them to limit water entry.

The water itself is unlikely to do anything, but if it enters and then freezes (or snow blows in and than thaws and re-freezes) it can start to enlarge the cracks.

If you are in a warm area it is another path for insects to gain entry (including termites).