And here's the thing. It sorta happens to all of us. Even when you take time off. I am moving to a new house and trying to do all the updates to the new house and freshen up the old one.

What's that got to do with guitar?

Well, I just bought a new acoustic (Taylor Grand Auditorium cutaway...weee) and, of course, wanted to play the heck out of. Since it's been a while, blister city on my ring finger. I know better. It's kind of my lead 'bending/vibrato' finger. And if it's been a little bit, that bad boy will get a blister. Not so muc when I just chord and fret...bends for me....

So it happens to all of us.

So my advice is to stick with chords and strums. Toughness will come. Also, I mostly agree with wolf on this point 'If you develop a blister, let it pop'. I do just pop mine right away and flatten it out against the skin. It mostly readheres. The is not medical device and I assume any doctor would be aghast. Though I wouldn't always say to go back to playing. Depends on how much you overdid it.

That said, callouses take time and playing.