All of the training the USAF has given me in both M-9, M-16, and M-4, have all emphasized using the first pad on your finger for trigger pull. Going to the second pad, past the distant joint, I hear the CATM folks refer to as "booger hooking".
If you think about it, you will be the most accurate with the least amount of energy you impart to the rifle. That first pad allows a light touch. Getting into that second pad now requires more squeeze to trip the sear using more of your finger, imparting some side-side motion if you are not careful.
There are some great shooters on here, with many NRA-certified instructors floating around. I am sure you will get some more valuable information shortly.