Canvas Imperfections - Now What?

[Leslie Ficcaglia]

I use a wide range of canvases but prefer the medium to the finer portrait texture. Occasionally I will find when I'm well into a painting that there is a slight imperfection in some crucial spot in the form of a small bump caused by the weave of the canvas. I can usually work around it or conceal it but I'm wondering whether there are tricks that others have come up with.