AWD LOCK and REVERSE

[Qashqai]

Today I was cleaning the inside of the car (and waiting my wife to be prepared) at the parking lot, while the engine was running. I left the parking lot by reversing and I heard a strange noise (not normal, compared to the engine sound I heard everyday). Then I immediately looked at the control panel and the AWD Lock light is on. I (stupid me) pressed that switch while dusting the car.

I looked at the owners manual and it says:

When driving straight, shift the AWD LOCK switch to AUTO. Do not operate the AWD LOCK switch when making a turn or backing up.

Do you think I damaged a power train part??? I just drove in reverse for 3 meters (from parking lot to the street), but I don't know...There is nothing wrong with the car for now.

I thought the AWD can be locked if the car is stuck in the snow/mud. What happens if the car is stuck, but you need to go reverse (say, there is an obstruction in front of you)? Why reverse + AWD LOCK is not recommended?

[TaiLuu]

The Rear Differential is probably suppose to go only direction and you turned it the completely opposite direction.
I could see why cause it's a tiny Differential....
It's really hard to tell if you really damaged the Diff.
I mean 10ft isn't really that much.
Sorry, thats all I could really tell you at this point.