Problem cleaning spark arrestor

Hey all,

So I figured I would clean the spark arrestor…well that didn’t work out too well. I took the muffler cover off then tried to remove the 3 bolts holding the tailpipe on. I must have stripped them or snapped the nut off inside the muffler because all they do is spin now. Can’t get them to come out. Now the exhaust has a rattle and it’s bothering me.

Any ideas?