My dog is unable to fully up left eye no discharge visible at time

Hello, we came home tonight and let our pups out of the kennel, they went outside a few minutes to use the restroom and right back inside. I noticed immediately that our 5 year old Min pin eye wasn’t opening all the way. He would keep it like this and sometimes closed all the way. I wiped it with a clean warm towel to make sure it wasn’t stuck shut and it’s not. I don’t see any discharge either. Any idea what is going on or suggestions to help him? Is an emergent vet needed? Thanks so much in advance.

Hello - please treat this as an emergency until proven otherwise.  There could be a foreign body, an ulcer, glaucoma or some other source of considerable pain and there should be no possibility of any of those being left for a significant time.  Of course, it could also prove to be fine to leave for 24 hours, but we would strongly recommend that you assume the worst scenario and have an emergency vet check it over.