what is this?

my son is 3 weeks old. he keeps waking up with this crust on his left eye and only the left. really started being this much crust and noticeable today. i’ve been wiping it with a warm cloth. i just put some breast milk on it after wiping it off after i took this picture. it does not seem swollen or red. no fever. doesn’t seem to bother him or be painful. so what is this? any ideas? do i need to take my son to pediatric urgent care tomorrow? or call his pediatrician? (it’s friday past midnight where im at) please help because i am worried.