By the looks of the picture that is not stainless. Seems like the hole is caused by an arc strike. It has also got a crack running away from it. You should drill a small hole at the very end of the crack to stop it going further. Clean it up with emery cloth before doing whatever repair you do. Seems like you could get someone to TIG weld it for $25 or so. If you go that way clean it up first so they don't have to charge you for that.