Somehow, a device lock password got set...either by you or someone else, but a human was definitely involved. Unfortunately, there is no way to bypass it. Only the created password can unlock it. There is no "master" or "override" password to bypass it. If you truly cannot figure out who created this password on your BB, then your only option is to fail 10 times, resulting in a complete WIPE of your BB, and you start over. Hopefully, you've been taking regular backups and/or using a Desktop Organizer (e.g., Outlook) as your master data source so that you can recover more easily.
Occam's Razor nearly always applies when troubleshooting technology issues!
If anyone has been helpful to you, please show your appreciation by clicking the button inside of their post. Please click here and read, along with the threads to which it links, for helpful information to guide you as you proceed. I always recommend that you treat your BlackBerry like any other computing device, including using a regular backup schedule...click here for an article with instructions.