First bonehead mistake. Need advice.

[Bill Bess]

I agree with Ron, you can just abandon or remove the old line (as much as possible) and install a new one, it's kind of what they do with buried pipelines...... but this ain't no buried pipeline.
Most importantly, relax, have beer and tell yourself...Hey I really installed that grommet in the perfect place, too f-in bad the gas line was in the wrong spot, I'll have to move it.
Cheers! Bill