my guitar injury?

The top knuckle* on my left ring finger is irritated, and I'm trying to figure out if it's because I have been playing the guitar incorrectly. I am asking for anyone who is reading this and either plays guitar or has expertise in orthopedic medicine to opine. Another possibility is that the irritation is due to a bug bite -- possibly exacerbated by my guitar-playing. 

I'll get to the bug bite theory later. But first, some explanation is in order. The A chord is one of the first chords I learned when I first took up the guitar. You make the A chord (first picture) by using your index, middle and ring fingers to hold down the D, G and B strings on the second fret. The B chord, which I didn't learn until later is essentially the A chord transposed by two frets. You make it (second picture) by holding your index finger across all six strings and using your middle, ring and pinky fingers to hold the D, G and B strings down on the fourth frame. And, of course, you can make other major chords by transposing this arrangement any number of frets up the neck of the guitar.

But I've gotten into what may be proving to be a bad habit. I now make the B chord using just the index and ring fingers (third picture). I'm using the index finger across all six strings, the same way I was taught. But I use my ring finger alone to push down on the D, G and B strings. I do it with the upper section, and bending that top knuckle backwards, in a way that it really wasn't meant to be bent. And sometimes (fourth picture) I use my ring finger in a similar fashion to make an A chord -- though I don't do that consistently.

Naturally, one may wonder why I started playing this way. The answer is that I find it easier. Most of the time that I play I'm using a ¾ size guitar** -- long story -- and it can be difficult to crowd three fingers on the narrow frets -- especially when I'm playing further up the neck. I also have a couple full size guitars, but the miniature one has the best sound of the three. I make the A chord the incorrect way (despite having enough room on the second fret) because of one particular song. In that, there's one place where I move from A to C#. It's easier for me to make that transition if I start with the one-fingered form of A.

Anyway, on Monday this week the joint was sore and red, and it hurt to play. So I've been laying off the playing this week, which is really annoying. When I'm working and I need a quick break I like to get up and play a song or two. But I pretty much like to stick almost exclusively to songs I wrote myself (or cowrote), and almost all of them (and all of the recent ones) involve this particular chord shape.

But part of me wonders if this is a bug bite. I was working in the yard on Sunday, moving some rotting logs. These were covered with ants, spiders and other creepies. On Monday I had several bug bites on my hands. And they were sore -- annoyingly so. The knuckle-sore was the worst of them, but it could just be a coincidence -- or it could be that that's the one bug bite that I further irritated with my guitar playing. I do note that the knuckle seems to be getting better just as the bug bites on the rest of my hands are getting better.

Opinions? Am I destroying my finger by playing guitar wrong? Will my finger fall off? Or is it a bug bite that will run its course in due time?

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*Fun fact: Researching the proper terminology, I learned that it's called the "distal interphalangeal joint." Woohoo!

**The Taylor GS mini, with koa wood