4 month old waking up in tears?

my baby is 19 weeks old and just woke up 45 minutes after laying down for bed and we let him fuss it out for a few minutes then i came in once he started crying but for the first time his face was covered in tears. is there a reason for this?

he hasn't had any sleep regression issues (only wakes up once or twice a night) and isn't teething. he also wasn't hungry, i nursed him and he fell asleep immediately. just curious if this is some kind of new leap or something that i can be mindful of?