hole in my head

looks like alot of milling, but I dont think alot was taken off where the hole is, since that would be the upper part of the chamber. looking at my heads, it looks to be close to 3/8" thick right there. It was probably a casting flaw (air bubble). I would take it to the machine shop and have it pressure tested if it passes i would run it. What about having a machine shop put a cylinder head crack repair pin in the hole?