Arm Injury

Hi, Obvioulsy I am new to this forum and I am also new to swimming. I have only ever been able to swim Front Crawl and so have been concentrating on this. Over the past three weeks I have swam probably 5/6 times a week and have managed to get my head under the water and have started to breath in some sort of partly correct fashion. Thing is, last night I was swimming medium pace (not very fast or hard) when I had an almighty pain in my right bicep area. The pain was unlike I had had before and at first I thought I may have momentarily dislocated my shoulder! My muscle felt pulled out of place, almost twisted. After a few minutes I felt ok to swim again, and, although a little uncomfortable, it felt ok. Today it has felt as though I have trapped a nerve or something. Does this sound like the result of very bad technique to anyone? Or just bad luck? I miss not swimming when I don't go but don't want to cause any more damage by going back into the water like this. Thanks for looking at this post. Amanda