Damaged Baby Chestnut Tree advice

Alright! I am not an arborist and I don’t know a whole lot about trees.

However, 3 years ago a squirrel left a chestnut in my flower bed (will be moving him eventually) and it’s been growing ever since. Unfortunately, this passed winter, my spouse ran over him with the snowblower!!! I was sure he was a goner but this spring a new ‘stem?’ ‘branch?’ has sprouted from the base of his little trunk.

So my question is what should I do with the bigger, but dead part of this little guy? Leave it alone? Cut it off? Thank you in advance!

tree pics