Hi It may be due to tmj disorder You need to examine clinically and radiologically  the tmj after that the cause can be ruled out and can treat

Clicking sound is from Temporomandibularjoint near ear while closing n opening your mouth.might be due to impacted upper third molars or Any Temporomandibularjoint disorder.

Hi. This condition mostly is because of the wisdom tooth that is probably impacted or covered inside the bone.. commonly found at the age of 18, the sound that u mentioned is the clicking sound.. kindly get a full mouth x-ray (OPG) done and consult a nearby dentist. U may require disimpaction of wisdom tooth, can be confirmed only after seeing the x-ray and correlating it with the clinical scenario..

Generally this kind of popping sound may arise due to the joint tmj near the skull n ear. Keep a check whether it causes pain or sound increases in future then you will have to get it checked by an oral surgeon or a dentist near you.