Any ideas on why random scratches are appearing on my arm?

Any ideas on why random scratches are appearing on my arm?
It’s nothing big just some minor scratches for some reason though this whole week I’ve just been randomly getting bruises on my legs. Yesterday when I was playing some video games with my friends and took off my jacket that’s when I saw these scratches on my arm it’s probably nothing important but I just wanna make sure. thank you! (Now looking at my arm closer there’s a few more scratches once again I know this probably doesn’t matter at all but just making sure to be safe.)
Any ideas on why random scratches are appearing on my arm?
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