Is there a natural cure for proctitis?

Depends. Depends on the kind of proctitis - infectious/inflammatory - radiation induced/etc - medical treatment is safe.
It depends on cause. Pain and irritation could be infection? Related to sex?, or inflammation like crohns disease or transient from irregularity---need to know all the symptoms-how frequent? When? How long? --need to look inside to see if ulcer? Inflammation, other lesions---could benefit from steroid suppositories or other anti-inflammatory, stool softners? --may need surgery it there is finding on endoscopy.