Pain is a big one, yes. An external stimulus causes immediate physical or emotional pain, but then there's the halo of suffering we make around the pain, which is representational, anticipatory, retrospective (and self-propagating and we might need therapy/coaching to let that go). I touched on this in my memoir on the theme of when thoughts become bothersome. Overthinking is signs about signs about signs.

Please ignore the object/non-object terms if they don't resonate. I recently stumbled across them within the art theory I mentioned, which has these discourses: Could this thing be sold as a useful object, and if not, could it be displayed in an art museum? In other words, does it have capitalist value and/or would elite art-appreciators categorize it alongside other capital-A Art they already appreciate? If not, then what is it and what value/meaning does it have? If the perceiver feels they're encountering a mystery, the thing they've encountered is a non-object. (According to the art theorists' proposal of that term, as I understand it.)

"Mystery" might be a better term. Theologians use it, an association you may or may not find wonderful, as it can be an intellectual hedge for weak links in a conceptual argument. (e.g., bunch of false premises + invalid arguments = "a mystery!!! hallelujah!!!") But if "mystery" is used to point out the non-concepts behind concepts...?