Yes it is better to weld a new plate back on there to cover up what you cut off, but it isn't completely 100% required. There are some who don't weld a new peace back on. If you're rubbing right now, and need it to stop right now, take a hack saw, sawzal, or whatever else you can find that'll cut through steel and just cut it off. Thats it. You're done. Personally, I'd try to get it welded back up, but as I said, it is not required of you.