Pretty sure that’s not the issue since I’m playing on a Madcatz SFIV tournament edition stick(the 20th anniversary one to be specific).
Blew out my finger again this weekend. It’s really perplexing since it’s just my right index finger and that’s honestly the finger I use the least.
How hard are you hitting buttons? Sanwa buttons just need a light tap, don’t need to sanford hands the thing
The problem is not the fucking arcade stick. All you’re doing is tapping a button, and not even that. Go see a doctor, you probably have a problem with your finger itself.
Or, it could just be neurological and you’re imagining pain where there is none 
Sounds like a healing injury like a fracture, sprain or strain. Probably not from SF. Switch to pad or simply don’t play for a few weeks and see if it comes back?
My thumb only feel pain because I use concave buttons. During the game, I would mostly tap the edge of the button
The fact that you say its the finger that you use the least hurts tells me quite a bit. All your fingers are connected. the most likely explanation based on my experience with slight of hand, flourishes, piano, and many other activities requiring digital dexterity. Is that you’re not relaxed and you are on your way to injuring yourself very seriously. check the following things:
clenching - are your muscles engaged too much ? really your muscles should only be engaged for the split second you touch the button. If you need to hold the button it should be done by the weight of your finger/hand rather than “pushing” with your muscles.
pressure. do you feel any pressure on yourwrist / pinky / thumb? (or anyhere else) this may be caused by muscles being engaged like i said earlier, but it could also be an awkward positioning of your hand. make sure your wrist doesn’t resemble a car/trailer jackknife your wrist should be relatively aligned and straight.
You could also be pushing down on the base of the stick with your wrist while trying to push your buttons. this restricts the movement of the fingers, and while you are pressing the buttons you are forcing your fingers to work much harder than they need to be. free up your wrist and use them to assist in the motion of pressing the buttons.
of course there could be many other things, but it’s a place to start, and again from my experience doing / teaching many skills requiring microdextarity I feel that this is the most likely cause (some muscle somewhere in your hand is engaged too much and when it shouldn’t be. without actually being there and looking and poking at parts of your hand im not going to be able to identify which muscle it is. but try to be more aware the next time you play. if you feel pain STOP IMMEDIATELY.
Also, i’m not a doctor, take my advice with a grain of salt. also. you should consult a doctor.