Didn't think that one through all the way, huh?
You will most likely have to cut the barbs with wire cutters and remove the fish. Catch the Peacock and put a "Lip-grip" on him, keeping his gills at least partially submerged if possible. Cut the catfish's spines as close to the base/body as possible and do NOT touch the Peacock's gills at all. There will be 3 spines, 2 pectoral and 1 dorsal.
Once the spines are cut, you may remove the catfish UNLESS you feel it will cause more damage coming back out than just letting him swallow it from that point. We have no way of knowing this, so you will have to use good judgement, based on how close to the body you were able to cut the spines.
It will be helpful if you have a 2nd person grab the severed spines with a pair of hemostats and remove them before they are accidentally swallowed.
In the future, avoid feeding anything a catfish dinner.
Use some stress coat afterwards as this will undoubtedly cause him a lot of stress, add a tablespoon of salt per 5 gallons of tankwater for it's healing properties and leave the lights off for a few days , only turning them on to check on his recovery rate. Melafix or Pimafix could come in handy as well, again as a healing agent
First, use your head next time.
Second, get a pair of forceps and bust the spines off the catfish while you hang on to the p bass.
lol you make it sound so violent. Busting sounds like it will cause further internal damage to the gills and mouth and throat. A good sharp pair of wire cutters is much safer IMO.....longnose if possible.
.....but yea, I agree it was not a very smart thing to do. Poor Peacock