Looks like a broken off radiator drain plug . Had you coolant changed recently? Take a look at this:
https://www.autozone.com/cooling-he...g/dorman-radiator-drain-plug-61136/102857_0_0
AutoZone
Dorman Radiator Drain Plug 61136
There are several body drain holes that use that plug. 1 behind each rear wheel behind the plastic bodywork, I'm not sure where else.