Hello! Thanks for putting your query in HCM. I am a Gastroenterologist (DM).
You have to strain because due to pain your external sphincter did not open up due to anal fissure
So what all you have to do is:
1. Take sitz bath
2. Apply ointment containing notroglycerine or diltizem per anus, before and after defecation
3. Make your stool soft by taking some laxative if it is hard
I hope I have answered your query and this will help you. Remain in touch and get-well soon