Quick fix: Recast on using a needle one size smaller just for the cast-on row, then switch to your project needles for row 1.
What you are seeing
The first few rows look stretched or floppy. The cast-on edge is visibly larger than the fabric above it. On hats or socks it gaps open.
Why it happens
- Too much yarn between stitches when casting on
- Needle used for cast on was too large
- Inconsistent tension across the cast-on row
Fix it now
- If project is small: rip out and recast on, holding yarn more firmly.
- Or: go down 1-2 needle sizes for the cast-on row only, then switch to project needles.
- If mid-project: thread a strand of matching yarn through cast-on loops, pull gently to tighten, weave in ends.
- A crochet border worked into the edge can also stabilise a loose edge without ripping.
Prevent it next time
- Use a smaller needle for casting on as a default
- Try the German twisted cast on for a firmer, more elastic edge
- Test a few cast-on stitches on a swatch first