It seems that you feel pain after passing stool. There are varieties of causes which can lead to such condition. As per the photograph, you might be suffering from Anal Fissure. So, first step is to keep you stool soft using some laxatives, then you can use some ointment which acts as an local pain killers.
Next Steps
You must visit a Proctologist.
Health Tips
Don't go for Self Medication.