The atlas to occiput joint does not pop like the lower joints do. Please be very careful with self adjustment to the cervical spine.

Is the NUCCA chiro treating your upper neck ? They use the posture measuring system to diagnose atlas (C-1) mal-alignment.

The NUCCA I saw had me ice before leaving his office because the adjustment he was trying to achieve was extremely sensitive to inflammation. Reducing inflammation maximized the value of each treatment.