Good to hear there is a hog there. Males will also take bedding into a nest box. It is probably more likely at this time of year to be a male, because they tend to return earlier from hibernation – having usually gone into hibernation earlier. The females are sometimes up to 2 months later to return than the males.
If you are going to make another box, or when the hog vacates this one, the only thing I would suggest is that you make some ventilation holes if you don’t already have them. My wooden boxes even have ventilation holes as well as the entrance and it is more likely that plastic could get condensation.
Good luck with the hog/s.