Its Clearly Anakin Skywalker's Lightsaber given to Luke skywalker by Obi-Wan Kenobi in a new hope , and which Luke lost when his hand was chopped of by vader in Bespin fight , Looks like the black kid found it when the hatched open an luke fell to the antenna
Yes, I know about the lightsaber. No, Finn does not find it.
The lightsaber is the McGuffin of the film. It lands on the desert planet Jakku. It passes through the hands of a few people until it ends up in the hands of the Vicar (Max von Sydow). He knows what it is. He contacts the Resistance led by Leia. The Resistance is a splinter group of The New Republic that is more militant. The New Republic is led by Mon Mothma.
Leia sends X-Wing pilot Poe Dameron (Oscar Issacs), to retrieve the lightsaber. The First Order intercepts the transmission to the Resistance. Kylo Ren wants his uncle's/grandfather's lightsaber for reasons that are still unknown. Dameron hides the lightsaber in his droid, BB-8, and sends it off into the desert. Dameron is captured by The First Order but freed by Finn in exchange for taking Finn with him so he can defect. Finn is not a pilot. He needs Dameron to escape. Dameron and Finn steal a Tie Fighter which you can see in the second teaser trailer.
I can give you guys the entire synopsis of the film if you want it, but I just wish one could put things in
spoiler tags on this board.