A weird bug... please help me!

hi! I went into the slice tool by accident, and then I couldn’t debleat my slice, my mouse became a blue square, and when I clicked anywhere on the screen a bug window popped and in there was written “cannot modify the sprite. it is used by another commend. massage type: 13.”
what happened and how to fix it? thank you so much!

please someone… my aseprite completely broke:(

I guess you tried to uninstall then reinstall?