Bicycle Mechanics - Dinged chain stay

A few weeks ago while riding my lovely old Bianchi as a fixed gear I dropped the chain on the inside, between chainring and chainstay. Luckily I didn't go down. At the time I noticed that the paint was really scraped but didn't notice much else, looking at it from the outside. Yesterday I was looking down at it from above and realized that there is a pretty healthy ding in the chain stay, about 1 to 1.5 mm in depth and the width of, well, a chain. Should I be overly concerned about this ding other than rust prevention and the operator stupidity that caused it in the first place?
Thanks,
Raymond

Unless there was penetration, it probably isn't cause for concern. However, there's a small chance that it might have affected Drop Out alignment. Which may or may not be of concern --depending on how fanatical about perfection you are.
Other wise, just put a piece of inner tube over the chainstay to protect it in the future.

Since chainstay failure will not cause you to crash (or even strand you), keep riding and enjoying the bike. Do check the area periodically for cracks, etc.

Hmm... Well, I am not one to disagree with John E, but I have been on a bike that broke due to metal fatigue under very similar conditions as Raymond describes.

I was on a tour and noticed that a small cut/scrape in the frame started to form a hairline crack extending beyond the cut. The crack expanded, got deeper, and by the end of the day, the tube completely cracked in half.

That sucked especially so because I was on an unsupported tour at the time.

Very sorry to hear about your Bianchi, Raymond, because I know you are in love with it.

I wonder if you could have the damage welded to prevent further damage.

Thanks, guys. I will keep an eye on it and get my LBS buddies to check it out and give me some suggestions. After reading your replies I went and took a good look with the aid of my little LED headlight. While there is certainly a VERY slight depression or, to use a more technical term, "mushed" spot and some paint scraped, it appears that at least part of what I thought was the depth of depression (sorry, couldn't resist) is optical illusion from a spot of whitish primer showing through. Definitely does not look like anything close to penetration or cracking. I will still get it checked soon.

Maybe I need to adopt Mike's approach and keep numerous old frames around as spares. Oops, I already do! :D
Regards,
Raymond