My shabunkin lived in a 500 gallon pond with other goldfish. Two weeks ago I noticed it was not acting right so I pulled it out of the pond and isolated it.  It looked like it had dropsy (swollen and pinecone looking) so I medicated the water and now he is acting and looking just  fine. His appetite his great and he's swiming around like nothing is wrong.  The only thing is he has a bump on his side.  Should I be concerned about the bump. Should I put him back into the pond (temperatures are in the 40's here) I attached a couple of pictures to show the bumb. I have no idea what it might be.

The water temperature is probably too cold to put the shubunkin back in.  There's a good chance he won't make it through the winter in his current condition so you should keep him inside until the pond water is warmer.