What a wonderful poem. This seems to be an evocative scene from childhood. The last two lines and the words at the end of them seem a fitting end to this short piece. The poem describes the activities of a boy playing in his neighborhood, but no friends or companions are described. He is imaginative and his games are full of fantasy and adventure, but the language hints at vulnerability and pain (licking of wounds, frail as a mayfly) and his ability to imagine himself in a nicer place than where he is (squatting in the "foul weeds of the vacant lot").
The last two lines, as with many sonnets, create a profound image which offers a new perspective on what has come before. These lines hint at the boy's loneliness and need to belong, as he is waiting for "someone dear to come" and bring him home. The image "whip him down the street, but gently, home" may hint at the boy being punished or whipped (maybe for staying out too late?), or it may simply be the image conveyed by the boy imagining he is being conveyed home as one might "whip" (or throw) a ball or other object (like the paper plane mentioned earlier) into the air. Home is where the "someone dear" lives, and the poem suggests the boy is happy for this feeling of belonging he will experience after a day of playing in solitude.
By the way, in doing an internet search on this poem I came across a wonderful blog that shares many, many modern and contemporary poems that you might enjoy. I have put the link below.