עַל־כֵּ֡ן לֹֽא־יֹאכְל֨וּ בְנֵֽי־יִשְׂרָאֵ֜ל אֶת־גִּ֣יד הַנָּשֶׁ֗ה אֲשֶׁר֙ עַל־כַּ֣ף הַיָּרֵ֔ךְ עַ֖ד הַיּ֣וֹם הַזֶּ֑ה כִּ֤י נָגַע֙ בְּכַף־יֶ֣רֶךְ יַעֲקֹ֔ב בְּגִ֖יד הַנָּשֶֽׁה׃
Therefore the children of Yisrael do not eat the sciatic nerve that is on the hollow of the thigh, to this day, because he touched the hollow of Yaakov’s thigh on the sciatic nerve.
Torah Temimah points to Chullin 96a.
גיד הנשה שנתבשל עם הגידין או עם הבשר בזמן שמכירו מגביהו והשאר מותר.
A sciatic nerve that was cooked with other sinews or with meat: if it is recognizable, one removes it and the rest is permitted.
Practical rules for when the gid is cooked together with other items.
Derash on the practical application (Bavli).
If the sciatic nerve is identifiable after cooking, it is removed and the remaining food is permitted.