is it possible for an intestinal worm to bite your anus?
No. But it may cause an anal itching (pruritis ani) which with scratching can cause tiny tears that may contribute to a burning sensation or pain. However, this is not the only cause for anal itching and it may be advisable to speak to your doctor. A stool test will be able to identify the presence of certain “worms” and your doctor will then be able to prescribe the appropriate treatment. Once this has been successfully treated, the irritation to the anus should cease.
You may want to read more on the treatment of anal itching in this article :