Get some glue in there, with as little water as you can get away with, then bind it tightly (with parcel tape would be my recommendation) while it sets, then knock it in so it's as close to level as possible. Make it totally level with a bit of sanding and it sould be good to go again.Personally I'd also apply a scuff sheet and wrap the bottom in tape just for a bit of extra support and so you can't see the repair