Knit has the following meanings:-
1. A method of using yarn and needles to create a series of joined loops which will be part of something; for example, a pair of socks: “I will knit a sweater for my younger brother and present it to him on this Christmas.”
2. To mend or to cause something to grow together: “The movie had a well knit plot which didn’t mar our interest even for a second.”
Nit, on the other hand, means the egg laid by lice or other parasitic insects: “These days many shampoos are available in the market which can remove each and every nit from our hair.”