The first thing anyone should do when experiencing pain in your hands from playing is to stop playing.  Pain is not good in any context when it comes to playing music, I've heard people say that they just play through the pain, take Ibuprofen and deal with it like a true "musician warrior".  Well that is the worst thing you can do.  I've been down that road in the past and I'm here to say that didn't work out so well for me.  Throughout the years had I stopped, I may not of had issues.  What had prevented me from stopping most of the time was I was always under a time crunch to learn several new songs or while I attended college, just preparing for a proficiency test.  There will always be circumstances such as these that will drive you to think that you have to work through the pain.  Resist I say and remember to take frequent breaks, if needed after your done, put some ice on the areas that hurt. 

Before you play a single note you should stretch out your forearms, hands, and fingers on both sides. It doesn't take that long and I now find myself stretching throughout the day just to stay loose which has helped me tremendously.  I came across a helpful link posted by cragginshred on YouTube.  It has now become part of my daily regiment.  I think he brings up great points in his video and he appears to be quite knowledgeable on the subject of physical therapy.  There are others out there as well and you should explore to see what works for you.   

I never was a vitamin/supplement guy but I've come to learn through doing research and asking people who live in that world what their feelings were and their recommendations.  I don't like prescription drugs if there is an equally natural alternative. I've never been a "pill popper" and pharmaceutical companies scare me to death.  What I mean and you may think differently, the side effects from taken an anti-inflammatory drug as an example, sounds worse than the actual pain. I've found that natural herbs and remedies while not as potent in some cases get the job done with little or no side effects. I'm not a doctor! I'm a musician, so I'm only speaking of my own experiences here. If you are on a regular medication speak with your doctor prior to taking any supplements or vitamins because it could possibly cause you harm.  

• Tart Cherry Extract 475mg (1/Day) for inflammation.
• Magnesium 250mg (1/Day) for pain caused by possible nerve and muscle damage.
• Glucosamine+Chondroitin+MSM with Manganese and Vitamin C (4/Day)  for joints and arthritis.

If none of these recommendations help relieve the pain then you need to go see an Orthopedic Specialist.  I've gone to several of them prior to this regiment who where located in my area and had a number of tests performed.  It would be beneficial if you could find one that specializes in musician injuries, but they are hard to find in most areas.  The doctors that I saw were not musicians but sports specialists and I don't believe they truly understood my concerns.  Most people are told they have Carpel Tunnel Syndrome or slight nerve damage either in their wrist or elbows.  My experience is that once they diagnose you they should provide non-evasive treatments prior to any surgery solution.  If those don't work then you may require surgery to repair or move nerves.  I would think long and hard about that solution. People that I've spoken with who had nerves moved in their elbows or wrists say that the healing process is very slow.  Also, they've expressed concern with sensitivity of feeling and dexterity.  Their outcome had mostly improved over time but with a cost of a year of not playing.  If your a working musician that may be a non-starter.  In some instances depending on the repair playing may be just like starting all over again.  Surgery in my opinion should be avoided or postponed and used as a very last resort.

I hope that I've provided some useful information that is helpful in maintaining and dealing with your pain.  Music should be fun and you should be able to enjoy playing pain free until your dying day. I'm not a medical person just a musician so a doctor trumps everything I've written.  I just wanted to pass along what I've been doing that has helped my situation.  Good luck to you!