Welding might work, but you'd be faced with essentially having to re-fit it like it was a brand new part, which can be tough.

Jack First is now manufacturing new replica critical Colt revolver action parts like the hand and cylinder locking bolt.

Personally, before welding I'd buy a copy of the Kuhnhausen Shop Manual from Brownell's and a new replica hand from Jack First and just start over.

One issue with welding and other expedients is that the small Colt's are almost always defense guns and that's something you don't want to chance a failure on due to softening of the steel or other problems.

You can try welding, but I personally wouldn't trust my life to the gun.
If you go with welding, give the gun a good work out and report back how it stood up.

One thing I failed to completely explain in the original post was that you get a chisel and grind the face flat, then lightly round the edges and polish.
Going back and reading it, I made it sound like you used a SHARP chisel.