It is perfectly normal for just one joint to be problematic after the incident you mentioned. Capsule/ligament injuries take a very long time to heal. Are you warming the joint up before climbing and warming down afterwards?
It is perfectly normal for just one joint to be problematic after the incident you mentioned. It is not possible to accurately diagnose capsulitis from the information you provided. It may be perhaps a ligament strain or volar plate injury. As to why it was worse indoor climbing - nature of plastic holds, higher volume of climbing indoors to out, trying harder moves indoors??Stiffness in the morning would probably indicate inflammation - i.e you've overloading the joint again. Are you warming the joint up before climbing and warming down afterwards? Which finger is it btw? Range of motion/mobility exercises are probably a better bet than stretching. If it is a ligament/capsule issue these tissues are not keen on being stretched! I'd keep it simple - warm up the joint ( and body) sufficiently, ease back on climbing or certain types of holds/climbing if you are getting marked morning stiffness and don't progress your climbing until this eases up.
I had a very similar thing years ago, it was especially bad after climbing indoors. Got to a point that I thought climbing was over, a few medical professionals tried but only got as far as the capsule was inflamed.I was at a yoga class and the instructor noticed my fingers were not straight in downward facing dog and that the area post knuckle wasn't getting any blood flow. After permission she straightened them. Finger felt much better after and after several practices of getting my finger straight in downward dog the inflammation went. My 2 cents but I'm not qualified in anything related.
The stiffness was particularly acute the day after an indoor session, but wasnt noticeable after an outdoor session. Any ideas why? Then it sort of just went away over the winter, so gradually that I didn't really notice it. A few weeks ago, it came back; still just the one knuckle, on the one hand. I can't think of a particular incident that provoked it, and its not a huge issue as I'm reasonably confident it will go away again in time. However, its bloody stiff this morning after a session last night, to the extent I could only make a fist with discomfort this morning. It does wear off though.Any thoughts on this? Anyone have anything similar? Does it sound like capsulitis? The weird thing for me is that its limited to just the one knuckle, on one finger, on one hand, whereas a lot of people seem to have more chronic issues with knuckles across multiple fingers. Cheers for any thoughts.