Finger pain and BH throw woes

I have had a bit of time of from throwing since before the Aussie Open and went for a proper throw yesterday for the first time since January. Most of the time things were okay apart from a few shaky forehands (RIP tie dye beast) but on some of my backhand throws, my index finger feels like it is catching on release and I am getting a bit of wobble on the disc before it flattens out. The wobble doesn't worry me but this morning, second knuckle on my index finger is super tender and painful to touch/bend/grip a disc. :(

What have I done and how do I fix it?