Small cracks and dents can be easily repaired with a bit of wall putty. Spread a thing layer with a putty knife, let it dry for a couple of hours than sand it with a fine grit sand paper. If the crack is a deeper one, you can follow this good tutorial. https://youtu.be/kZy_eTMggVU
Hi B, Here's a how to video that may help: https://www.youtube.com/watch?v=kZy_eTMggVU
You could try Flex Seal if it isn't a badly cracked wall
HUH?! HA! HA! Flexseal.
Here you go! I believe this will help you a great deal as well.