There is no "under the edge" on the H2O. The bezel is glued to the display. That's what makes it "waterproof" (whether you trust a bit of glue to hold back water is your own affair). If you poke holes with a needle


, you've damaged your water seal and if you damage the bezel (the shiny part) you risk the loss of touch screen functionality.
I recently got a broken Kobo Touch from Ebay (lower third of the display still works) and it had a lot of "dustbunnies" sitting under the edges (Kobo Touch actually has an edge you can put your fingernail under, the H2O does not)... what I did was fold a piece of paper into a V shape and remove the dust in the corners with the point of the V.
Paper should be less likely to cause permanent damage than needles but you should still try a soft cloth first. Or just ignore it if it's only visible at 200x magnification and does not affect function.