TL;DR: It happens, who knows why, but it's usually clinically insignificant.
The usual visible result of a bee or wasp sting is wheal or hive formation, the itchy, swollen and reddish bump we have to contend with after the pain subsides. Cold compresses and allergy medications are effective not only in reducing itching but in speeding resolution as well; even without such measures, wheals commonly resolve spontaneously within hours or sometimes days.
Most stings are caused by the more aggressive members of the order Hymenoptera, specifically wasps. Hymenoptera venom contains components which cause inflammation and components responsible for allergic reactions. The hive typically caused by hymenoptera venom is inflammatory in nature. The allergic reactions are uncommon, and cause large local reactions of 10 cm or more (LLEs, about 10% of stings according to the literature but much less than this in my experience) or systemic reactions (anaphylaxis, much rarer, and, even more rarely, other serious reactions as well).
When the venom is introduced into the skin, the proteolytic enzymes begin to degrade the surrounding tissue. The release of histamine from mast cells and basophil activation, in response to the venom, causes vasodilation and the ensuing inflammatory response: edema, pain, erythema, and increased warmth.
Inflammatory responses are normal and a necessary part of healing, however, their resolution represents a delicate interaction between multiple mediators. Sometimes there are missteps, and inflammation continues beyond the expected, "normal" process. A common example often occurs in healing open wounds, e.g. burns, abrasions, incisions, etc. In that case, there's an excess of granulation tissue which must be removed so that the process can start again. This is easily accomplished when the tissue is on the surface, but when it's not, it becomes a mass (if it's small, it's called a nodule) called a granuloma, and other means must be used to limit it depending on the cause, e.g. if it's an infection, antibiotics are administered. However, sometimes the cause is not obvious, and if the granuloma is clinically significant or worrisome in any way, other means are used.
What do care-givers do if there's a granuloma that's not clinically significant? Nothing. It's not significant. It's not worrisome. The overriding goal in medicine is "First, do no harm."
A common example of this type of granulomatous nodule is a non-infected foreign body, e.g. the result of a "road rash" injury where small bits of macadam might be too difficult to remove without doing more harm than good.
The tissue above heals over and a fibrous tissue capsule surrounds the granuloma, which slowly heals as the tissue undergoes reorganization. The end result there is a scar containing dark bits, what used to be called a "road tatoo" before the rise in popularity of tatoos. They are usually clinically insignificant, and removing them would be doing harm (of course that's subjective. By that definition, plastic surgeons do harm all the time.)
Should the victim just be patient for the wound to heal or is there perhaps a more serious concern that should be checked out?
While most times healing is uneventful, any inflamed tissue can undergo granuloma formation*, including tissue trauma secondary to wasp venom. It's rare, but it can happen. There might be a tiny foreign body beneath the skin surface, there might not. The key to "what to do" depends on it's clinical significance; if it seems harmless and isn't causing any problems, a watch and wait approach is taken. If it bothers you, if worrisome symptoms appear (pain, growth, signs of infection, etc.), if they arise spontaneously, or it seems to be the new way your wounds heal, it's time to see a health care practitioner.
*For example, lung granulomas are commonly found on imaging studies done for other reasons. Lungs are exposed to a lot if irritants which cause inflammation.
Hymenoptera Stings
