No way around it if you forgot. Once you enter it incorrectly 10 times, the device will automatically wipe everything as Penguin said.
Now, if this device isn't really yours and you found it someplace, please try to find the rightful owner. And please take no offense at that statement, because we get a lot of similar questions from people who find BBs and want to make them their own. We have no way of knowing how legit you are.