I'm not going to call it Werehog specifically since your OC could be a different species.

Here's what I could come up with.

Bite scenario: You went out with Sonic for the night, only for Sonic's Werehog form to return. But this time, he's more savage than last time. When you tried to get away, he pinned you to something and bit you. What happens next?

Curse scenario: Little do you know that a witch had cursed for all your life to become a Were(species). This always happens whenever the blood moon comes out. What happens when the curse takes effect for the first time?

Dark Gaia possession: Dark Gaia is jealous of his brother's , Light Gaia, ability to go out and be among the people in a smaller form. He wants to walk among the people who worship him. He then finds you and learns that you were born on his celebrated month, making it possible for him to use you. What will happen when he finds you?

If you don't like any of these, make your own scenario!