It sounds like Feynman remembered that his student thought highly of the problems he was working on late into his career. Feynman's encouraging his former student, as a recent graduate, to start out with low-hanging fruit.
He goes on to describe some of the easier problems that he worked on in the beginning of his career. That gave his former student some examples of worthwhile problems to start out with.
Personally, I think Feynman was very humble. Especially for a Nobel Prize winner.