When I was working at a deli, I had to use the meat slicer a lot and I developed a bad case of tendinitis. The restaurant owner's dad happened to be a doctor, so she sent me over to his office for an after-hours exam. After he checked out my arm and wrist, he wrote me out a prescription for a strong anti-inflammatory medication and ordered me to stay off that slicer for a week or so.
While I was there, I pointed out several bumps I could feel under the skin of that arm. He said they were ganglia cysts, probably triggered by the muscle strain on that arm. He said they could be lanced and drained, but it was not strictly necessary. He said they would either go away on their own or wouldn't be anything but a nuisance. A lot of people have wrist ganglia and don't even realize it.