Like they said looks like its time to fab a new section in there,and since that spot looks like that i would check the rest of the frame over while i was at it.

Also i would not recomend stick welding it. For a frame you should use Mig or Tig at around 120-140 amps. Stick welders have better penetration but on something like a frame with a "thin" (1/8-3/16") wall tickness its very easy to blow right through it.