I was just watching TV and realized my eye felt really funny. Almost like it wasn't opening up all the way, just really weird.

So I got up and looked in the mirror, and my eyelid is swollen! Not around my eye, not under my eye, just my eyelid. It's super swollen and I can't open my eye all the way because of it. When I touch it (with my eyes closed), it feels like a marshmallow. It's all squishy.
My eye isn't red, everything else seems normal. It doesn't hurt, and it's only one eye.

Any idea what the heck is going on?