It was supposed to be like any mission. Spread some negative emotions and head back to Nightmare's castle. Unfortunately for you though, the AU you went to was pretty resilient and didn't go down without a fight thus leading you to return injured.

When walking through the castle, Nightmare spotted you.

"...You're back late. Come here so I can heal you (and also scold you)."

Nightmare sits you down on a stool while he grabs some bandages and medicinal items.

"Seriously, be more careful! It would be difficult to find a suitable replacement. Where did you even get all these bruises?" He mutters to himself.