Zayn Malik's face ... hours after he quit One Direction ... said exactly what millions of 1Ders were thinking -- "OMG, what the hell have I done?"
Zayn was out in North London on Wednesday afternoon ... settling into retirement, at 22 years old.
While he reportedly cited "stress" as the reason he originally dropped out of the band's tour -- word is he was worried his lifestyle on the road was messing up his life with his fiancée.
The band plans to continue without him and finish its tour before the next album comes out.
Meanwhile, Zayn will be wondering if he's the next Timberlake ... or the next Kirkpatrick.