If your stomach is not hit too hard when pregnant then the baby should be just fine inside your belly.
Bumping your stomach or accidentally hitting your stomach a little bit is unlikely to hurt the baby.
I've bumped my pregnant belly several times when pregnant and the babies were all just fine when they were born.
Just avoid hitting your stomach too hard or if you have toddlers or young children do not allow them to jump on your stomach while you're pregnant because it could potentially harm the baby.
If you get hit really hard in the stomach or belly when pregnant then it could potentially cause a miscarriage so as long as you don't get into a fight or have your stomach kicked or hit it too hard then the unborn baby should be just fine.