Hello and thanks for the query.
I understand your concern and will try to tell you different reasons for causing anal burning and pain after bowel movement.

Burning in the anus or rectum, or a burning sensation during or after a bowel movement may be a symptom of a number of conditions. Some of the causes may
Spicy Foods
The chemicals present in spicy foods typically causes irritation of the tongue mucosa where it detected as being ‘hot’. This effect persists as it travels through the gut. If these irritants are not degraded or neutralized by the time it reaches the rectum, it will cause local irritation of the anal mucosa. The inflammatory response also causes redness and sometimes swelling of the affected area. The most common irritant foods is capsicin present in chilli and peppers but a host of other chemicals in foods can have a similar reaction. The burning sensation usually starts after a bowel movement and persists for a period of time afterwards. Spicy foods may also cause mild diarrhea which can irritate the anus and lead to burning.

Anal Itching

Pruritis ani (itchy anus) is often associated with excessive wiping, certain foods and sometimes skin diseases and infectious conditions. Repeated scratching of the anus due to itching may lead to a burning sensation. This is often aggravated after a bowel movement.

Poor Hygiene

Inadequate wiping and bathing can cause local irritation of the anal mucosa due to the presence of fecal matter and large populations of bacteria

Hemorrhoids

Hemorrhoids are the swelling and weakening of the rectal veins, often associated with chronic constipation or diarrhea. It may also arise for other reasons. Hemorrhoids, also known as piles, is a common rectal condition and presents with a host of symptoms like rectal bleeding after a bowel movement, especially upon wiping, itching and burning. It is aggravated after a bowel movement but the discomfort (burning, itching, pain) usually persists throughout the day to varying degrees.

Anal Fissures

Minute tears in the lining of the anal mucosa often arise with chronic constipation and diarrhea. 

bowel problems like
Inflammatory bowel disease
Constipation -  impacted feces
Irritable bowel syndrome (IBS)
Gastroenteritis
Rectal prolapse
Other complications like a perianal abscess or anal fistula may also cause burning in the anus or rectum and needs immediate medical attention.

Other Burning Anus Causes

There are host of other causes that may also contribute to a burning sensation in the rectum and around the anus which may or may not be associated with bowel movements. Some of the causes may include :

Skin diseases
seborrheic dermatitis
psoriasis
eczema
pilonidal cyst
Infections
Sexually transmitted infections (STIs) – genital herpes, gonorrhea, chlamydia
Other infections – intestinal parasites, candida (immunocompromised patients), streptococcal dermatitis, tinea crura/corporis (fungal)

You should consult a Gastroenterologist and get the diagnosis made because unless and until proper diagnosis is made,proper treatment is not possible.
In the mean time before you consult the doctor use xylocaine jelly before going to toilet and zinc oxide ointment afterwords.
I hope to have answered your query however you can revert to me for any other query.
Thanks and best of luck.

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