Flashing light on my dash

I am hoping that somebody can help me with this, because driving is hard!!

The other day, there was a flashing light on my dashboard. It stayed on for like a long time. I think it may have been on for about 10 miles, but then it went away. It was a green arrow pointing to the left.

Any ideas? Could it be serious? Do you think I should take it to the dealer? Thank you so much!