Didn't realise it was an auto.
I had a friend who killed his 1.3 Nova gearbox (NOT AN AUTO) changing down to 3rd instead of up to 5th, it was only for a few seconds

It was the gearbox which took the brunt of the force and started braking up over the next few weeks - the garage said an oil change (top up mainly as it was really low) may have saved it.
If the gearchange is not smooth it could indicate low gearbox oil. I still think its worth checking the gearbox oil but HDI is right - there is little chance of long term damage in an auto box.