Hello,
Yes you can do llb after you complete your bsc. You will get enrolled for 3years llb program as you have already done graduation. There are many good colleges from where you can do.
LLB itself a higher degree course. But still if you are son interested in law only then you can go for LLM. It is a master degree in law. After that you can also go for Phd. But these are far ahead things.
So, if you really wanna do llb then find good college and get yourself enrolled for it.

All the best !!