Quick fix: If the slip is on the current row, slide the slipped stitch back to the left needle and work it normally. If it is one row back, tink to that stitch, work it, and continue.
What you are seeing
One stitch looks taller than its neighbours, creating an elongated or stretched column. If the stitch was slipped knitwise (twisted), you may also see a crossed-leg stitch directly above it. The column can look pulled or distorted compared to surrounding stitches.
Why it happens
- The needle accidentally passed over a stitch without engaging the yarn, so no new stitch was formed.
- Distraction mid-row caused you to slip a stitch that should have been worked.
- A pattern slip stitch (intentional) was confused with a plain knit or purl stitch, leading to an unintended slip.
Fix it now
- Identify whether the stitch was slipped purlwise (not twisted) or knitwise (twisted) by checking whether the legs of the stitch cross.
- If slipped purlwise and you are still on the same row: slip the stitch back to the left needle purlwise and work it as normal.
- If slipped knitwise (stitch now twisted): slip it back to the left needle, reorient it so the leading leg is at the front, then knit through the front leg.
- If the slip happened one row back: tink back to that stitch, re-work it correctly, and continue forward.
- If several rows back and the stitch is only elongated (not twisted): thread a tapestry needle and ease the extra length into neighbouring stitches along the row; block the piece to even out the tension.
Prevent it next time
- Read pattern notes carefully to distinguish an intentional "slip 1 purlwise" instruction from a regular stitch.
- Place a locking stitch marker directly below any intentional slip stitch position on the previous row so you can tell at a glance which slips are deliberate.