First thing is to get back in. Open the chrome bar on your keyfob and slide out the manual key.
Then go to the car door and prise off the last quarter of the chrome by inserting the key into the slot you’ll find underneath and twist - the chrome quarter should prise off to reveal the key slot. Insert your key and twist, then pull the handle and the door should open.
Once inside, try starting the car in the normal manner. If it doesn’t start at all - no dash lights, windows don’t work door lock won’t lock, then you have a flat 12V battery.
When this happened to me, I had a booster battery pack - NoCo - so I popped the bonnet, connected the battery, then started the car. After disconnecting the booster, I left the car in ready mode - this charges the 12V - for at least 20 mins whilst I put the chrome quarter in the door handle back - not an easy task.
I think the alarm would need to be reset for which you’ll need an OBD monitor which connects to the car’s data port and will allow you to reset all the errors.
I’d go straight to your dealer though to get this sorted out, as it looks dangerous to have an airbag alert when it hasn’t deployed. HTH.