I have been playing guitar seriously for a few months now and in the hand that I use on the guitar (fretting hand) my left index finger has developed a bump on one side near that PIP joint. I have also noticed that it is getting more swollen over the top of that joint too. I also have a slight bump in the same area on my left pinky finger. I am finding it hard to believe that at my age (16) I could develop arthritis from playing guitar. Keep in mind that the only symptoms I have are in those two fingers in my left hand. I have been icing them 1-2 times a day for 15 minutes as well. I also have not had an injuries to these fingers. I have stopped playing guitar for about a day now and am going to give it a week to see if it gets better. What do you think it is though? Any thoughts? Ways to treat at home?