The branch is very unlikely to "heal itself", so cut it off. Sticking the loose branch back in the ground will probably not work, but it's worth trying. Fothergillas root very easily as long as they don't dry out.

Don't worry. Fothergillas are tough plants which sucker and spread from the roots - sometimes a little too agressively - so yours will be fine next spring and beyond even if it's too young to blooom next spring.

the simple rule.. on any plant.. is that broken or damaged branches are removed ...

there is no plant specific requirement on this ...

and that would include any branches that cross and rub on each other.. causing a festering wound ...

most shrubs ... once fully established.. can nearly be run over with a truck .. and live [though they may not be pretty for a few years.. lol]...

so anything a 5 year old can do is considered minimal ... shrubs .. by my definition are just that hardy .... unless you are collecting foo foo plants to show off your gardening achievements.....

but that doesnt include your plant ...

what would have made time stand still is if your 5 year old was hurt .. the damage to this plant is irrelevant ...

ken