Don't worry, keep on talking to your child in Cantonese whenever you are available; he/she will pick it up very soon.
Unless your child goes to a nursery in which English is the only language, otherwise you will be amazed how much and fast he/she picks up Cantonese in school.
My son learnt mainly English vocab before 2.5 yrs old, but once he started going to nursery, the improvement in Cantonese was obvious.