I just happened to stumble across this post. I am a retired hand therapist and have treated many trigger fingers. Once the "catching" gets to that point you might be able to release it by totally relaxing the hand and using the other hand to hold down the big knuckle /fully bent position while gently pulling the smaller knuckles straight. This of course is a temporary fix.
I recommend seeing a qualified hand surgeon who may opt to first try a steroid injection or recommend a surgical release. The surgical releases that I saw were very successful. After a surgical release (or maybe injection) see a certified hand therapist to learn tendon gliding exercises and scar mobilization techniques to maintain your range of motion. It's important to get and keep the tendon gliding. The therapist can make a splint to allow/promote this tendon glide. An immobilization splint in "straight" position, might be indicated for night use.