Probably means the ligaments in the arm is not strong enough yet for the weight you doing. If keep going you might tear it, takes 6 weeks to heal, in which time you can't do any exercise that involves that arm, unless you do physio to help it heal faster, in which case you go for 4 weeks healing time.
You need to get the ligaments to get stronger, and sadly hypertrophy is not the way to do it. Focus a bit more on compound movements that will force you to bulk up better, which strengthens muscles, ligaments and even the bone structure. This is more in the range of 3-5 reps. For curling, a pull exercise is best, like barbell rows, or pendlay rows and pull-ups. For me, this still get my arms/biceps plenty tired, so by the time I get to curling, I don't have to go too heavy.