Cap of toilet water shut off valve is too small
Hi, I just noticed that the cap of the water shut off valve of my toilet is not big enough to cover up the entire hole on the wall so there is a small gap on the wall. I suspect (and hope) the plumber probably drilled the hole too big when they installed the toilet (my place is 10 years old).
Could anyone let me know how I can cover up this crack/gap please? I've seen insects climbing in from this crack. The attached picture shows the crack circled in red.
Thanks a lot for your help.