There must be inflammation at the swelling site, and purulent blood is the product of immune response in the body. After discharging purulent blood, wipe it off with a sterile cotton ball, disinfect it with 70% alcohol, and then wrap it with sterile gauze.

There are many reasons for this:

It may be that the catgut embedding material is not absorbed and antagonizes your immune system, or that improper operation when it is used for catgut embedding leads to irritation and injury.

It is also possible that the disinfection of buried thread is not thorough, which leads to bacteria being brought in and inflammation.