If generating a generic nylon worm, you can get away with;
(nylencased), bodystocking, (encasement, encased:1.3), mummified \(bound\), arms behind back, (tan/black cocoon, pantyhose), legs together, bondage, faceless female, (faceless),
legs together, bondage may not be required, but better to be safe than sorry.
If you want a photo-realistic look, add realistic as a prompt. If you want it to be more anime/cartoon looking, add realistic to the negative prompt.
If generating a specific character, you need to do a bit of extra tagging;
(nylencased), bodystocking, (encasement, encased:1.3), mummified \(bound\), arms behind back, (tan/black cocoon, pantyhose), legs together, bondage,
from there, you can add your character prompt, be it a simple set of tags or a character LoRA. Any prompts relating to clothes should be omitted. From here, you can add blindfold and improvised gag tags as needed. Remember to remove eye-related prompts if you're including a blindfold.
If you want the head to be covered, you can try adding
faceless, faceless female, head covered, pantyhose over face,
But be prepared to fish for a good seed, it can be hard for the AI to properly put a face under the nylon.
You can also add bound arms, bound legs, bound wrists, bound ankles, nylon rope, to add bindings above the cocoon.
Lastly, the AI has a habit of making the captive completely naked. If you wish to add extra clothes under the encasement, you can try adding panties under pantyhose, bra under bodystocking.