can i also say my friend introduced me his sister?
I really think this sentence needs 'to' before 'his sister'. And then it's exactly like it was mentioned in the comments above.
Yes. "to" is needed for one or the other of the two persons. Just like the need for the Dative in Polish.
Why can't it be "My friend introduced me to his sister"?
I don't understand the above comments regarding this.
Because "introducing" can be somewhat directional.... "Hi, Mim, this is my sister Kate" as opposed to "Hi, Kate, this is my friend Mim". Perhaps....