From Gary Martinez:
If your kid is sensitive or defensive to the seam in front of their socks it's likely because it can feel like a stabbing feeling to children's toes. This can be extremely uncomfortable and a major distraction, throwing the kid off all day until solved.
Here is one way to help: your kid may just like to be sockless because of this--it is a natural way to problem solve the seam issue. My daughter Monica used to be this way a lot in her earlier years, and I eventually had to accept it because she was happy, and she knows her body best.
Hope this was helpful, and if you need a few more helpful tips you can send me an email to: garymartinez650@gmail.com. You can also find my book here.