who was framton and why had he come to the rectory

We are never given details as to who Frampton Nuttel really is. All we know is that he suffers from a nervous condition and has come (been sent) by his doctors to spend some time alone and het much needed rest.

"The doctors agree in ordering me complete rest, an absence of mental excitement, and avoidance of anything in the nature of violent physical exercise," announced Framton, who laboured under the tolerably widespread delusion that total strangers and chance acquaintances are hungry for the least detail of one's ailments and infirmities, their cause and cure. "On the matter of diet they are not so much in agreement," he continued."

Who was Framton Nuttel and why had he come to the rectory?

Framton Nuttel was a person who was suffering from a nervous condition and he was sent out by his doctors to spend some time alone and had needed some rest.

He had come to the rectory to meet Mrs. Sappleton to present one of the letters of introduction.