in Edit > Preferences > Interface, you can change the size of the icons
If you click on the little arrow on the far right of the palette, you
will also find options for making the palette fields larger.
If that's not large enough yet, I think there's a forum thread
somewhere, where someone else posted a workaround... or you could wait
for the next major Inkscape version (1.0), which is due some time next
year, which supposedly fixes the issue.