You could remove all of the other standoff screws, and then start putting them back in loosely. Then perhaps the one in your picture can be lined up. If that works, then you could go around the motherboard and slowly tighten the screws a little bit at a time. This may force the case back into shape, but it could put some stress on the motherboard, so you can try this at your own risk.
Many builders first assemble the entire pc outside of the case, on a non-conductive surface (wood, cardboard). Then if it boots up and everything works fine, assemble it inside the case. This allows you to see that everything is plugged in securely (like the graphics card is seated fully in the Pcie slot. Sometimes it is harder to see if everything...