Mine fell off a chair too and manged to release her 3 point harness, don't know how. She cried, I did all the checks made sure she is attentive, alert, responding, breathing normal, eating and drinking, sleeping, Interacting as usual and didn’t cry after again.
If it’s stressing u out then that’s all the reason u need to get him checked out x
If it helps you feel better ur not alone my son is also 8 months and fallen off too and I’m sure a lot of mothers can say they’re baby fell off too. Take the height of which he fell off into consideration too
My baby has rolled off sofa in sleep and is constantly falling amd bashing her face amd gets red marks but usually go after a lil while if not gone down by tomorrow could rake him as precaution but if fi e in himself and dinesnt cry when touch it should be okay but any worries can always go see one