Hi. I'm online and happy to answer your question today.
It sounds like a bruise to me
Bruises on the eyelid are very common and since the skin is so thin the bruise shows up really well :) Most times an isolated event like what you are taking about is from some minor trauma that you don't even remember.
As long as you have no other symptoms or lots of bruises elsewhere, I would not worry about this at all.
It is also important to know that it may spread and change colors some.....this, too, is nothing to worry about.
Does this make sense to you?
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