I get a little bit of bursitis in my left (bridge) shoulder every now and then. If it's bothering me and I'm planning on playing for a few hours, I try to remember to take an anti-inflammatory before starting. Seems to help.
Other pool injuries:
I'll occasionally pull my final backstroke just a little bit too far back on my break shot, then proceed to smash the tip into my thumb or bridge finger.
A few weeks ago, I was practicing my closed-bridge, head spot break. I practiced it for so long that I developed a nasty little blister on the cue side of my middle finger. I had to wear a glove for almost a week, just to shoot regular shots.
Last week in league, I broke too hard and knocked my cue ball onto the adjacent table. It landed almost on top of my league teammate's cue ball, right as he was shooting. That was a close call, but thankfully nobody was injured.