Can a person with anal fissure that has taken medication to heal the tear have anal sex after a long while let's say 2-3 months after the wound healed?

Yes: Just be sure to use a lot of lubrication (unlike vagina, anus & rectum isn't naturally self-lubricating). Also plan to ease in (no pun intended) b/c abrupt stretch can lead to another tear. Of course, it's always wise to wear a condom to minimize risk of stds as well as common bowel flora (greater risk of bladder/kidney & prostate infection from anal sex w/o condom use than vaginal/oral route).

Yes, if healed: The risk for anal fissure is having excessive stretching of the anus, either from hard bowel movements, or from anal trauma, such as anal intercourse. This can be prevented by gentle stretching of the anal canal prior to intercourse and sufficient lubrication. For those with fissures due to constipation, it is important to take stool softeners and regulating frequency of bowel movements.

Yes: If the fissure has healed then with the right care then it is possible.