Hello Jeff, and Welcome to the Forum:
If the wall has no load on it, it may be possible to push it back in place. The more realistic method would be to prop up any load, remove the affected blocks and re-lay them.
If we are talking about a retaining wall, it may be necessary to take it out including the footer and start anew. The footer should be at least 3' wide X 1' deep with 2 #5 re-bar 1' on center each way, mats placed top and bottom. Plus "L" shaped bars tied to the bottom mat and extending upward 32" on center. Lay the blocks with a bond beam in the third row and the top row; each having 2 #4 bars the length of them and concrete poured in the cores with the vertical bars and in the bond beams. A run of 2" cap blocks that are 2" wider than the blocks (1" protrusion on each side) will make a nice, permanent wall.