As well as being exploited by a Chinese hacker crew, it has now been added to the Magnitude exploit kit, which enables amateur malware authors to build all manner of software which could make your life difficult. There's already been some attempts to install ransomware on some computers.
Adobe have confirmed that the flaw is being jumped on by hackers, especially those using Internet Explorer on Windows 7 and Firefox on Windows XP. Even if you aren't using these things, you should still sort your life out and update your Flash.
If you prefer, you can just get rid of Flash. As most computers come with it built-in, even though it isn't the crucial thing it once was, this means hackers are always tempted to attack it.
If you're using Chrome, your browser updates it automatically. If not, click here to see if you have the latest version of Flash and, if you don't, update it now.