Originally Posted by Kernel Crittenden

The front sight on a -3 is a pinned on black ramp. It's carbon steel that's been blued. Get a cold blue touch-up pen, and re-blue it.

Otherwise, punch out the pin, and replace the sight with a new one. S&W sells them, but you may have to drill a hole in the new blade. I think they come blank -- without being pre-drilled.