Help! Have I just broken my husband's Pajero?

Dear all. I am so upset as I could have just destroyed my husband's Pajero... It's
2011 model (Exceed). My 4y.o put the transmission into 4HLc gear (instead of
4H), and I didn't notice it. So I backed up from the garage to the driveway, and
was slightly turning the wheel to turn onto the driveway when I felt that the car
is almost not moving ( I was driving very slowly). I then put it into Drive and
drove approximately 20m forward before stopping. I then changed the gear to
4H. My husband said what I did was almost fatal to the car. And now no one
knows how quickly it's going to break, and how long it will last.. Is this really
that bad? If I take it to the mechanic, will they be able to estimate the extent of
damage, and fix it? Thank you in advance!