What Medication Is Suggested For Bug Bite On Left Butt Cheek?

Yes, I recently have experienced what seems like a bug bite on my left butt cheek and I scratched it because I thought it was just a little bug bite. Well its been there now for at least two weeks and it itches and has spread a little but its still on my butt cheek. I'm trying to figure out what exactly it is, and I do have dry skin so that could be a part of it, and also I have a pet. Can you help?