anal glands

[SandraOrtiz]

Would anal gland problems make a dog's anus gap and the outer anus swell...

[Margot49]

Hard to tell what you are describing.  It may be a prolapse and should be checked.

[Jerry_NJ]

Sounds like a "express" (think that is what it is called) of the Anal glands would be worth a try.  If you can't do it yourself a groomer may do it as part of a grooming - what $50 (depends on dog size and complexity) surely less than a vet check.  If that doesn't work see a vet.