The "Basic Instinct" star just shared a photo showing what appears to be a massive shiner covering one of her eyes ... which she apparently suffered on vacation in Turkey.

Sharon says ... "This trip has been tough; but I'm tougher."

Unclear where, when or how Sharon suffered the apparent injury ... but she doesn't seem to be letting it ruin a good time.

In a subsequent post on her Instagram story, Sharon shared an image of the backyard in her hotel room ... and there's a private pool with a patio and stone wall.

Yeah, she's balling.

Sharon's getting lots of love and support in the comments ... the replies are filled with well wishes and concerns ... and some folks are even saying she looks good with a black eye.