Hi, thanks for your query.
I can realize the the pain you are going through.
The pain and numbness
is due to damage of the superficial nerve
fibres due to the injury
by glass and while handling the tissues during stitching.
Since it is on feet, you are putting pressure on it while walking which increases the pain and delays healing.
The site may be red because it is still healing or there may have been some secondary infection. It is not a scar tissue as formation of a scar is a slow process.
You may discuss it with your doctor when you get there for stitch removal and start antibiotic if required.
Hope this solves your query.