Deion Sanders is showing how his foot is healing after having surgery 3 weeks ago -- by posting a gnarly photo of the bloody surgical wound.

Remember, the Jackson State football coach went under the knife in September for a dislocated second toe that he's had since his NFL playing days ... with the doctor saying "it's gotten worse" over the years.

The procedure went off without a hitch ... and the Hall of Famer was told to keep off his left foot for the next six weeks.

Halfway through recovery, Coach Sanders wanted to give a super-gross update on how things are going ... and if you can get over the gruesome stitch job, it's good news for the legend!

The 54-year-old posted a photo via IG -- you can see the stitches going up and down the first and second toe on his left foot pulling the bloody skin together ... and it's pretty gnarly!

But, it hasn't stopped Prime Time from coaching the JSU Tigers -- he's been riding a golf cart and this dope custom 3-wheel scooter during team drills.