Whether the testicle is removed or not, surgery in the scrotum will take time to heal. You may need to take pain medicine for a few days. Within a few days to a week, you should be able to return to work or school. It's helpful to avoid strenuous activity or exercise for several weeks.
You shouldn't notice the stitches around the testicles, and they shouldn't bother you. The stitches are there to keep torsion from happening again. Torsion of the other testicle can't be prevented by changes in activity or by taking medicine. Only sewing stitches around the testicle will prevent future torsion. If you feel pain or swelling, seek medical attention right away.
If the twisted testicle is left in place, it still might shrink a bit, since lasting damage may happen. Sometimes, if one testicle is removed, the other may grow larger than normal. This is known as "compensatory hypertrophy."