I'm not sure if it's ich....and I'd like to avoid placing him in a QT if possible.
I'm not quite sure why QTing fish is so undesirable. It avoids the very problem you are experiencing now potentially, and places no other livestock in jeapardy at the same time.
It only require an extra 15-20g tank, a heater, and a HOB
filter. A few weeks before you make your purchase, you place some filter floss or other media in your main tank's sump, filter, whatever. You then just set the QT up a few days before purchase and put the seeded media into the HOB
and you can often skip having ammonia and nitrite problems. You can then treat as mentioned above, although I favor no treatment unless there is an actual problem. After the 4 weeks of success, you can break the tank back down and store it.
In addition to being a great place to observe fish for disease, it is also a fantastic place to get a fish comfortable to tank life without the stress of other fish harassing it. I have found they start eating much quicker as opposed to the CB that you see hiding.
As much as it is your responsibility to provide a good, healthy home to your livestock, it is more
of a resposibility that they enter that home in great shape.
Hopefully, this experience is not ich or another disease and can just be a learning experience.