It is possible to swap two corners, but doing so will also swap two edge pieces. It is possible that there are two edge pieces on the cube that are identical, and swapping those two will not be visible, so that you can in effect swap two corners without seeming to have any effect on the edge pieces.
Notice that the centre square showing a 5 is twisted by a quarter turn. If you solve the corners relative to that 5, you'll find that you don't need to swap 2 corners, but that actually only one is in its correct place and you need to cycle the other three corners around. This also means that the four edges around that 5 are essentially all in the wrong location. You can put two of the edges correct by cycling 3 of them around. That leaves two edges that need to be swapped, which can only be done by also swapping two identical edges elsewhere in the cube.
To do this a bit more directly, you could use the following PLL move sequence (a J-perm):
This swaps the two corners in the right hand side (UFR, UBR), swaps two edges (UF, UR) and twists the centre to the left.