Intermittent eye pain

[TychosNose]

2yo ds keeps crying out in pain and touching his right eye.
It's a bit red and slightly swollen, but that could be from rubbing it when it hurts.

It's been going on all day. He'll be fine for a while then really cry out for a about a minute then it seems to go away.

He seems to be in a lot of pain.

Any ideas what it could be? He doesn't have enough language to describe the pain. Just keeps saying "eye".

[TendonQueen]

Is there an eyelash that's come off and slipped under the bottom eyelid? That can be really irritating but intermittently because if it stays still for a bit it'd stop. Hope it's resolved now.