How long is " along time ago" ?
I've had a similar injury twice - both times caused by doing pull ups without being fully warmed up AND dropping to full extension a little too quickly (not a kip though, lol) ... I remember thinking the first time I did it how bizarre it was to hurt your TRICEPS doing pullups ..
Really pull-ups were the only exercise that made my tricep feel that way ... It was sore, and I noticed it doing other things, but the pain was bearable/ minor on everything but pull ups - felt like my tricep was ripping off the bone if I tried one.
Never went to the doc for it so I can't help with a diagnosis, but I would advise you to drop them for awhile and do back exercises that don't aggravate it. If memory serves, the first time I injured it that way I couldn't do a pull up for about 2 months without some level of pain ... Second time around it was a little quicker, but I knew right away it was the same injury (to the same arm)
I recall being able to sub pulldowns without pain .... Albeit light ones.