Resistor selection based on power rating
Since 0.1 &lt; 0.162 it would be a bad idea to pick a resistor that is not rated for the actual nominal dissipation. 

For high reliability, or if the environmental conditions exceed what is in the datasheet for the rated power, you should derate the part. So 0.25W or 0.5W would be better (either would be acceptable in many situations, 0.5W would likely be larger and more expensive but probably a bit more reliable). 

Or you could change the circuit to use less power. For example, if the 2K is a dropping resistor for an LED, use a more efficient LED and increase the resistor. Or use a switching power supply to reduce the 18V to 5V and then the resistor might only be required to dissipate 20mW --  (5V-3V)*10mA.