who is knight?

Touchstone is telling Celia to go and see her father, "Mistress, you must come away to your father." Celia asks when anybody made him. a fool, an official messenger. Touchstone replies, "No, by mine honor, but I was bid to come for you." Celia asks where he learnt that and Touchstone launches into his tale about the Knight, pancakes and mustard. The short of it is that the Knight swore on his honour, yet this particular knight "had no honour", hence his comment on the pancakes was neither a truth nor a lie. Touchstone loved to play on words; he is clever and does this kind of thing for much of the play.

Oh yes, Touchstone's further meaning is that he indeed has honour so what he says is the truth.