Sounds great!!
But the 0 reading for nitrAtes is suspicious. If tank is back on track with the nitrogen cycle, that value should have increased from yesterday.

If you take the fish out to treat, you are going to put him through another dangerous ammonia/nitrite levels if your quarantine tank is not cycled, and possibly kill him.
By the way, what are you treating for and what meds? It may not be sickness, but just ammonia burning. If the fins are just torn and have fallen off and there is no bacterial infection or fungus that you can see, then a water change everyday or every other day will heal it just fine without meds and without moving the fish and stressing it additionally.
You should be doing regular water changes in this tank anyway until you are sure ammonia/nitrite stay at 0, the rest of the fish will benefit from it too. Just don't go overboard washing with tap water