What can be expected after treatment for testicular torsion?

Depends: If the problem was diagnosed and treated quickly (surgically), blood flow to the testis should have been maintained and testicular function should be intact. If treatment was delayed, the testicle may have "died" and lost function. See fp/surgeon about testicular function/blood flow tests.

TORTION: Tortion, after surgical correction or relief can result in a smaller, atrophic testis. Often the other side is tacked to the scrotal wall to prevent it from happening. Usually a few weeks of pain and activity restriction is required.

Pain and swelling...: Pain and swelling in surgical site are expected, but can be easily managed with reassurance and judicious use of pain medication with expected slow resolution in 1-3 weeks. Of course, individual postop course may vary.