02 sensor help

My forward o2 sensor fell out of the exhaust of my 99 Tacoma. From the look of the threads, its been lose for a long time. I plan on trying to wire brush them down but if not I have to take it in and get them changed for about 150$. I accidently dropped one of the new nuts down the o2 sensor hole and into the exhaust. Couldn't find it with a magnet or anything so I think it rolled down in the bigger part. Can I leave that nut in there? or will it melt? will it bounce around and mess things up? Cant open up that part of the exhaust because the bolts are so rusted I think they will break. Any help would be appreciated.

 

Don't worry about the nut.
this write up may help:

https://www.tacomaworld.com/threads/rear-o2-sensor-done.142451/

 

Won't melt. Rattles in a 99 Tacoma should be treated as 'charecter'. Think about it, Google it. Metal melting temps vs exhaust temps 4' down the exhaust. You'll be fine.