Lab teachers

I'm a first year student I have good grades and have past  all my clinical tests except the insulin syringe. I forgot to wipe the insulin bottle when I went back in other than that it was correct . The lab teacher was off the week prior and the sub passed everyone I get who is very nit picky. She said I failed and would have to do it again in front of two instructors and be videotaped for the head of the program. The instructor is so intimidating and I was so nervous. I just got a email I failed because they saw a tiny air bubble. It's two days before the semester ends I'm devastated I've had good grades and now I have to wait another year . I understand but I feel that was a lot not fair to fail me at this point lab is supposed to be a learning experience. I'm so devastated I'm not sure if I should talk to the head about it ?