Wow all these day's and know one has used the correct terms.
You broke the stud off. You well need to find a good repair shop and hopefully have them use a easy out to remove the rest of the stud.
They may need to put a insert in there for the new stud.
I guessing you didn't use any PB Blaster before you did this.
211,000miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. CHECK your oil, these cars use it.
Engine Build - Click Here