When I started working out, I had the same problem using only 3kg db's (yup, those are the girlie weights). For months, when I tried something slightly heavier (and that would be 4 kg db's, yup, still pink dumbbells) my elbow would act up.
So I had to be carefull about my elbow for months. Now I'm using 13,5 kg db for triceps extensions. So I've managed to sort out the problem.
My advice: whenever you feel bad pain (and we all know what good pain is), then lay off. Give the joint time to recover.
It's not like you need hughe triceps anyway. At least, not as much as you need your elbow.