As far as what to do about it. There have been many good suggestions from carefully filing by hand, to carefully grinding with a dremel or small grinding wheel in a drill to getting it reamed out.

Any method will work.

The steel is probably pretty hard, and filing by hand will be a pain, as well as difficult to keep the file in the right place, only getting the raised material, so I'd lean towards grinding it with the dremel or drill. Or, getting the proper reamer.

While the tubing is thin, it is substantial enough that it would take quite a bit to grind through it.