Thank you for these two names, so I've used all available Polish databases, including surname etymology, surname locations, geographical directories, place name etymological works, old and curent maps, etc., here is my work:
Both your family surnames Janicki and Nawrocki (Nawrocni is not from Poland) from the 19th century and earlier might be as Polish Small Nobles (Drobna Szlachta) from Masovia central province of Poland, many of them decided to sell part land and send the younger members of the family to the U.S. in the three waves of immigration in the 19th c, and the beg of the 20th c., to prevent them before military service and owful wars in Russian army where millions were killed, and to give them a better chance in their life.
Checking all places named "Grechowo" like Grochowo, Grochow, Grochowa, Grochy, etc. and collerating it with the "Fogoszelle" given in ship manifest as POB - Place of Birth (the correct in Polish is Pogorzele, Pogorzela, etc. (means "pogorzel" - the place in wood burn up to give place for a new settlement) I guess they might be following places as the origin of your Leon Janicki immigrated in 1909/19010 (why both years I will tell below):
1. Grochy-Pogorzele, gmina (commune) Zambrow, family ancestral RC church and cemetery is Zambrow, located in abt 100 km in NE direction from Masovian and Polish capital Warsaw:
2. Grochy-........., few villages in the same Masovia province, north of Warsaw, gmina (commune) Kozlowo, RC parich was Gzy:
3. Grochy-......., few villages in the same Masovia province, gmina (commune) and RC parish and cemetery was Poswietne:
As you see we must have a little more to locate your Leon's origin in Poland, maybe you can obtain his naturalizations papers (the petition and declaration of intent is the best giving for sure the place of birth), maybe other friends from our forum can check more American databases (WWI registration draft, SS-5, obituary, etc.
Checking more EI database I've found same name from Pogorzela/e (SIC?!):
Leon Janicki, arrvd NY port 1910, 18 y old, blonde hair, blue eyes, going in the US to father Franciszek Janicki 3350 Chicage IL, living in Poland mother Apolonia Janicka in Pogorzele, Russia (Poland), and be careful, there is And also:
Leon Jamicki (the correct is Janicki), arrvd NY port 1909, 18 y old, brown hair, blue eyes, going to the US to uncle Franciszek Janicki 820 Wall Str. Chicage IL, living in Poland Tomasz Janicki (father) in Pogorzela/Pogorzele(?).
From these ship manifests both Pogorzele are given as Pogorzele, Kal., and this confused me, as I've found also Pogorzela in Kalisz province, but this was under Germany then.
Please find more with American databases, we will try to help you more to find the correct Polish ancestral home with parish church/civil records and information about their beloved place of birth, childhood, and family past, all our ancestors deserve our memory about their family roots and heritage.