I would also suggest trying to remove it.
If you have the option, I would try a fish trap first. i would be worried that catching the fish in a net might cause the antenna to push deaper or tear whatever it's cough on. (it could be his gills if it's going in through his mouth)
once you have him out, just use gentle force to pull it out. Other than that it's hard to suggest a fix. You might want to consider vitamin suppliments in it's food if you're not already doing so, to boost his immune system to keep any scratches/wounds from getting infected. Your LFS
should have some supliments, like selcon or garlic additives.