I changed my Inkscape to a black theme. I also changed the icons to grey; this all came in a zip file that someone had prepared.
All was fine, however I saw that the icons were too dark and I couldn't see them properly. Stupidly, I opened the icons.svg file on Inkscape and changed all of them to a slightly lighter grey, not realising that this would break the whole program.
After this I re-opened Inkscape and the whole tool bar to the left was gone (had crosses in place of icons). I tried downloading Inkscape again and re-installing several times. When I first run it, it as the default version, but if I close it and open it again, the same problem happens as before.

Anyone know how I might be able to fix this?

Which version of inkscape ? On which system ? What was the content of the zip

Inkscape 0.91 on Windows 10. The zip contained some .svg files of all the icons