HELP!! SPLAT lusty lavender hair dye!!!!?

Hey, I have never dyed my hair before and I have some questions. Since only limited hair dying is allowed at my school, I am only dying a small chuck at the base of my neck. The rest of my hair is chocolate brown and goes down to mid back. I did the test run and only a little itching occurred after the bleach(I also have a mosquito bite around that area that might have been the cause). Would it be ok if went ahead with the dying without waiting the 24 hours? Also, additional advice would be great!