See this answer by the developer of Rufus:
Not much that can be done when Rufus especially indicates that "The device is in use by another process". You will need to find what process is accessing the drive and prevent it to do so. It may be a security solution or one of the software listed at the end of the FAQ.
Unfortunately, there's really not much I can do to help, as it's impossible to take a guess at what is causing the access issue. You may have some luck identifying what it is by going through every single running process in Process Hacker and seeing which one seems to keep a lock on your USB drive.
Before attempting to run Rufus, temporarily disable your antivirus software. If that doesn't help, see if Rufus will work for you if you restart the computer in "clean boot" mode. See directions here: https://support.logitech.com/en_hk/article/228 Don't forget to reboot back to normal mode when you're finished.