Ya’akov’s fight with the angel.
According to Ramban, Ya’akov’s fight with the guardian angel of Eisav alludes to the suffering of the Jewish people during the times of Exile.
The fact that Ya’akov was later healed completely (see below 33:18 and Rashi ibid.) indicates that when the exile finally ends there will be no remnant whatsoever of Jewish suffering. In other words, the key emphasis here in Ya’akov’s battle with the angel is not the injury that Ya’akov suffered, but rather, the fact that it was only a temporary injury.
Thus, when we observe the prohibition against eating the sciatic nerve (gid hanashe), our emphasis too should be a positive one. Namely, that rather than focusing on Ya’akov’s injury to the sciatic nerve, we should stress the fact that later he was totally healed, representing the ability of the Jew to withstand all the tribulations of exile and emerge unblemished.
(Based on Likutei Sichos vol. 25, p. 174; Sefer Hasichos 5751, p. 263)