When you're saying, "Yesterday I came from Lahore," it implies that either it is an answer to a question or it's an incomplete sentence, as in "Yesterday I came here directly from Lahore...because it was getting late." This is why the second sentence can't stand by itself; it is not an independent clause, if you want to get technical.

Secondly, these sentences are not the same. They mean very different things. I'll explain you with meaning.

First sentence means:
-I reached here yesterday (from Lahore.)

Second sentence means:
-Yesterday I came here directly from Lahore.

There is a difference of emphasis: The first sentence is about time (reached yesterday) and the second is about place (directly from Lahore).

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