My birthday is on 16/10/1990 bt my schol d.o.b is 16/10/1991 nd wnt birth certificate.wt I hv to do?

Do you mean college? If yes:
You need to inform your college of this immediately and bring whatever you can to prove that your born in 1990. The sooner you do this, the better. It will affect your exam cetiffcates etc if you don't.

If you're talking about primary/secondary school, then you can't do nothing about that really.