Maggots can survive inside of human skin and inside of human wounds. A maggot infestation of living tissue is called "myiasis." Some species of maggots, such as Cochliomyia, specifically infest living tissue in order to feed themselves.
Most maggots are harmless to humans under proper sanitary conditions. Myiasis is most common in tropical and subtropical conditions where there are more insects and flies with parasitic larvae. Most infections come from bug bites or open wounds, but there are rare types of maggots that actually burrow into intact skin. Infesting maggots create a lump under the skin where they feed until they're ready to hatch. Surgical removal of the larvae is the only available treatment method.