i hit the drivers side air bag where you put the key in to turn it off

ok any ways i was putting a wooded box in my cab cause it was raining and it wasnt that big i just set it on the seat well driving down the road i had to hit my brakes pretty hard to miss a dog well the box hit the air bag on and off thing and now my light is on

i want to know

1. what happened
2. why is the light on
3. and how do i fix it

i have no clue and i dont wanna spend alot of money to fix it