Your stomach ain’t ready for it yet. Vomiting forces the usual flow of what you’ve taken in to flow to the reverse direction and dragging things, like the acids in your stomach, with it.
It’s quite a shock for the body. Depending on the severity of the vomiting, it can take a little, until it’s ready to ‘take in’ again.
IANAD this is just what i experienced myself with vomiting in the past and what my brain made out of it.