My 6th baby clicked while nursing. My nipples were very painful.  I had been
working with breastfeeding mothers for 15 plus years, was an IBCLC and had
successfully breastfed 5 other children.
Thanks to Chele Marmet, she discovered he had food allergies to some things I
was eating. He was four months old at the time. His palate was itchy and  he
scratched it with his tongue.  Shortly after I removed the offending foods
from my diet the clicking stopped and the nipple pain disappeared.
Ruth Solomon