Since it can't be changed, u should all the more do ur best for
the subjects you have obtained. It would be a problem for you if
you intend to go JC and take a science course but if you choose the
poly route, combined science is all that is required to enter the
science courses.
Ur options are already limited and if you don't study hard and
do well, you won't even have any options to talk about in 2 yrs
time.