What do I do when a thought like this happened

A few minutes ago I was doing my chores while my mind started to think of this scenario where I was doing something innapropiate to someone and I had it in my mind for 30 seconds until I realized what was going on. I immediately shaked my head to get it away and now I’m frustrated and worried. The best way I could describe what was going through my head when it happened was like me going on Reddit, thinking of what to write and then that thought started happening, I don’t like this, I don’t know if this is an intrusive thought or this my doing, I need someone to tell me that I’m just overreacting