today was back n triceps day, everything was going good, i did my rope press down, skull crushers then i got to tricep kick backs n i just felt this sharp pain in the head of my tricep in my left arm, i continued doing kickbacks for 2 more sets of 8, and the pain continued, but it's weird bc i stretched it n everything n did all my other exercises fine without the pain ... improper form maybe? i dont know, this has never happened before! help please!