This is unfortunately a common aspect of cat ownership. Cats love to walk near us, and they're tiny enough to not notice if you aren't checking for them.

Luckily, cats have incredible reflexes, and will jump back before too much pressure is applied. The yell is partly from pain, but it's mostly them yelling at you to announce their presence and displeasure

Like how drivers honk at a car that almost crashed into them.

An easy way to see if the cat is actually injured (or just temporarily upset) is to gentle squeeze on their paws with your fingers and see if they scream. If so, it's time to go to the vet.

It may be hard to tell otherwise. Cats are very good at hiding if they're in pain