When the Guard Commander of the day next door to gym has a prosthetic leg after having his blown off by an ied you get no sympathy if you moan about a hurt finger, besides our instructor thinks Tiger Balm cures everything , even a broken arm, and he was a Combat Medic 
Thanks for all the replies, i eventually got the MRI scan and had to pay for it myself. Its not the most comfortable or quickest procedure - very noisy and i had to do a superman pose to get my hand scan as i wasnt keen on having my whole body in the scanner. I then had to make another appointment with the doctor. He essentially said i was fine and didn't need a splint or anything and referred me to hand therapy to get my finger mobilisation back but i am doing that myself. I think he said there was a bit of fluid build up in the finger and signs of tendonitis but i cant remember now. Im going to go back to training tomorrow though im sure the finger isnt straight now, it still has a noticeable bump to me and it is still a bit painful
If it's still injured don't train on it....especially in grappling where you are constantly using your fingers for pulling and pushing and gripping and of course the risk of someone's knee or elbow or their body dropping on your hand and making it even worse.
And use this time to learn to grapple without that hand. It’s not easy, but can be done. You’ll lose more often, but that’s where the learning lives.
Did you go back to training as you said you were going to, despite all the advice against it?
Maybe instead you should stop training like was initially suggested, both here and by the medical professionals you saw, rather than continuing to get new tests. Althout at this point, you've been actively training despite knowing you should be resting your finger, so you might have damaged it more and it might just be permanently bent from now on. Sucks.
