welcome to HCM!
Post coital bleeding can be due to CIN itself or it can be due to infection or Cervical or endometrial polyps.As about cervical cancer
,PCB occurs in 0.7-39% of women with cervical cancer. The risk of a woman seen in the community with PCB having cervical cancer is approximately 1in 44000 in 20-24 year olds and 1 in 2,400 in 45-54 year olds.
So go for the colposcopy
with a relaxed mind and wait for the results.
hope this will help.take care!