What can I do to reduce pain while crocheting?
So I'm a big knitter and crocheter and a musician with tendinitis for the past 20 years. Aside from the standard advice (NSAIDs, massage, etc) there are a few things that you can do to mitigate the situation. 

First, make sure that the amount of pressure you're using is the bare minimum amount possible. It may actually take some time to retrain your hands, but it's worth taking the time to do it. You may want to slow down a little bit, focus on using as little effort as possible, and then speed up gradually using the same amount of pressure. 

Second, with knitting and crochet you can also mitigate repetitive strain by making your movements as small as possible. This of course has an added bonus of making your stitches a bit faster.

Third, you may want to experiment with different styles and materials of hooks/needles. I can barely use a standard boye aluminum hook, but I find that when the hook has a nice handle, it actually helps a lot. The lightness of the hook and the resistance of the material will also make a difference.

The last point of advice that I have for you is that if you start to feel any pain at all, stop, stretch, and give yourself a few minutes before you go back to it. It might be kind of tedious at first, but if you avoid damage while retraining your muscles to move lighter, smaller, and with less pressure, you should be able to retrain yourself so that long term you can crochet without any pain at all. It took for me about 3 months to really fully go through the retraining, but it's made a HUGE difference in my ability to do all of the things that I actually want to do.