It's not a tumor . . . oh, wait, well, technically it IS a tumor

AH-ha! I knew it!
http://www.missionforvisionusa.org/anatomy/2006/06/what-is-conjunctival-hemangioma.html

The good news is that I was right. "Eye birthmark," or conjunctival hemangioma is what is on Zain's eye. It's pretty rare - and Zain's hemangioma is actually under the conjunctiva, in the next layer of the eye - but since the conjunctiva is clear, it looks about the same as the picture... however, Zain's is (luckily) under his upper eyelid - so nobody has seen it, except for me, and the doctors. The eye doctors were impressed with Zain's size and strength, and resilience. He didn't like having his eyelids pulled on, but stopped crying as soon as they were done checking him out.

The doctor said, "While 1 in 7 babies are born with some sort of birth defect, this one is a rare anomaly."
"You want to see an anomaly - check out his mega-toe!" I blurted out. I am happy that his visible birth defect is one that I think is cool, and the one that would look scary, is hidden under his eyelid.
He said there is no reason to biopsy it. Hallelujah! And it is not putting pressure on his eye, so no need for injections or other treatments right now. So really, it's no big deal. We will just keep checking on it every 3 to 6 months.

Not that I would ignore potential health problems in my children, but I am smiling and walking around thinking, "See, I told you so . . . sometimes, mom's just know"
I didn't know that it might just go away. The doctor said it's good that it hasn't seemed to change or get bigger since birth, and it might start to get smaller, and eventually dissappear.