As far as I know, the light gives you a signal there is a low voltage from the batterie.
If you got a good charge, around 14V, you're batterie doesn't work that good anymore. Chek the batterie or let it be checked.
I believe at some stores they chek it for free.
You should have some other things not working or the car won't start.
If everything works fine, fuse maybe.
Hope this helps