***** FILE SYSTEM WAS MODIFIED *****

Cause

This comment from the fsck(1M) command tells you that it changed the filesystem it was checking.

Action

If fsck(1M) was checking the root filesystem, reboot the system immediately to avoid corrupting the / partition. If fsck(1M) was checking a mounted filesystem, unmount that filesystem and run fsck(1M) again, so that work done by fsck(1M) is not undone when in-memory file tables are written out to disk.