Trigger Finger (or Thumb) is an inflammatory condition that is often related to Arthritis, Diabetes or a Thyroid problem - or in my case, a significant cut on my right index finger that caused some tendon/nerve damage almost 40 years ago left me with similar symptoms (but not inflammation)

If (prescription) anti-inflammatories have not helped then it "could be" more of a repetitive motion injury (similar to carpel tunnel but effecting the finger joint) so work with your Doctor to investigate other possible causes other than one caused by an inflammatory condition like arthritis or diabetes

That's what I think coz I experience it when I eat forbidden food, even fruit that I am not supposed to eat.