Yesterday I unplugged my cluster to change the light bulb and drove it without the cluster connected it (to let someone off the drive!)

When I reconnected it, the airbag warning light comes on for 2 minutes and then switches off.

Is this a fault or do I just need to pop into my audi dealer to get it turned off becuase I took the instrument cluster off?

My car is a '95 A4 1.8

Thanks