Go to Home Depot, get
-a small tube of ready-to-user plaster and
-a piece of sander (a little bigger than a soap bar)
-spray paint to match wall color
When you get home, do this:
-Fill the holes with the plaster, you may need to repeat it for a few times since dried plaster tend to shrink a little bit;
-Sand it smoothly with the sander, touch it up if needed;
-Paint the patch over with the spray paint, shake well before use.
p.s. Your rental office may be able to provide you with the plaster and paint, don't be shy to ask first.