Cut at the Side of the middle finger

Hi Guys,

when i play a lot in the week and use a lot of smashes i get a weird cut at the middle finger on the side. It always hurts when i smash and it is not affected by Drops, or any shots below the hips. Since i play a lot in the week (3 to 4 Times) the cut can never heal up and is constantly expanding. I have the feeling that it is mostly affected by the under arm rotation, that puts somehow a lot of stress on this particular point of the middle finger. Does anybody have experience with this?
Regards