"In your own good time," Thursday says. Time to recover and heal. Morse would rather return to work. The headaches and fatigue aren't the worst aftereffects of Emma's poisonous brew.
Staying in his flat gives him too much time to remember his journey through Hell. Only shadowy images remain, but those are enough to make him desperate for distraction, even tedious scutwork.
Nick Wilding wanted to see what lay beyond the door. The bloody fool didn't understand what Morse has known for years: there are doors in the mind that must never be opened, lest one release the monsters within.