I've had this on and off with Rocky. This is only our experience, maybe the experts here can give you more info.
She did have pink eye a while ago, but with that the fur around her eye got progressively wetter. It is apparently contagious between species (I got it from her) and can be part of a respiratory infection or possibly allergies. Rocky had a URI.
It's possible for them to injure the eye slightly (poked with a bit of hay,etc.) and scratch the cornea.
Either of those two possibilities needs a vet visit.
Rocky recovered from pink eye but has a blocked tear duct. She starts to look wet under the eye a day after her dust bath. She gets dust baths more frequently which seems to help. I also periodically clean the eye witha gauze pad and put in some saline if she'll hold still. There's nothing to be done to fix this, unfortunately.
HOWEVER - dust baths are a BAD idea if there's an infection or scratch. The dust will stick to the wet fur near the eye and could irritate the eye even further.
I would watch it until tomorrow and if it's still wet call your vet.