Do you have a cat or a dog? You could just say that you got scratched while playing. Hate to blame it on the family pet, but people probably wouldn't blink an eye at that.

I'm with Ifst that I'm reticent to give out excuses to hide self harm, but honestly, what I have found is that if I just say, I had an accident and brush it off, people tend to accept that and leave it be. Most people don't want to think of the darker possible causes anyhow, so they're eager to accept the easy excuse.

Thinking about having to hide cuts and scars is one of the things that helps me not self-harm. So maybe this will help motivate you when you feel like SI next time, that you will have to find ANOTHER excuse. It does get tiring.

I hope this helps.

Seesaw