Can’t be totally sure but could be from baby’s saliva or milk. Wipe off with clean water and apply breastmilk if available - usually works for me for any small bumps on baby’s face & neck
I also allow my LO to chew her hands for comfort. For the crying I think it’s usually gas in the tummy, sometimes that happens to my LO also and I will rub a very tiny tiny drop of ruyi oil on her tummy and do bicycle and she usually feels ok after farting then I will continue feeding. You may want to check with PD if it persists and he is not gaining weight well.
mochi