Sometimes from knocks that seem minor to your brain, but they just bust a small blood vessel inside - enough to give a little bruise.

I most often see them when moving boxes around, especially heavy boxes. The next day you see a few and don’t even remember hitting that part of you.

One thing that helps remind me where I got a bruise is pressing the centre of the bruise. The resulting pain links back to the pain you got at the time. I don’t recommend this though coz it hurts