Cannot figure out last move

[RBL]

Hey all, My son just got this cube for his birthday so we are beginners. Watched videos and played with it quite a bit. Trying to help my 8 year old finish his cube and we only have one corner left to solve. I tried putting this in the online solver apps and none of them give me a correct way to solve. The sides you cannot see are correct, just this last corner. If any one can help we would appreciate it.

 

[Cale S]

If only one corner piece is unsolved, the cube is not solvable just by turning it, you need to either twist the corner or disassemble a few pieces to solve it

 

[YouCubing]

have you taken it apart before? there are some positions that can only be reached by taking the cube apart and putting it back together.

 

[RBL]

Weird, not sure how that would have happened, but I see your point. We (he and I) did not take it apart or anything, but he did take it to school so who knows what happened. We will just manually move the square to fix it. Thanks