Thank you for the query.
Rectal surface is covered with a very delicate mucosa. Hydrogen peroxide
contact with this surface causes serious burning and destruction of it. Due to that, bleeding and bloody mucus appears. So this was not a good idea.
Healing of such burning causes an inflammation. Due to such inflammation, some rectal narrowing can appear (it all depends how deep was a burning).
I suggest you to visit general surgeon
for rectal examination
. It can take a week or so to get it healed.
Hope this will help.