Thanks for your query and the clear picture.
The picture shows the puncture site as black as the necrosed tissue and a large area of cellulitis around.
I would advise you the following:
Consult a Doctor and get a course of an antibiotic, antihistamine and oral steroid for a a few day.
Do not fondle the area.
If the string is inside the wound, it may have to be removed intact.
Take a injection of Tetanus toxoid.
Wishing you a speedy recovery.
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