Thanks for the query to H.C.M. Forum.
Green , watery diarrhea
may be due to fungus infection .
2nd reason may be due to bacterial infection .
In my opinion you got mild tear due to dildo just at the anal opening ( although you mentioned rectum
This tear usually not develops diarrhea.
Plenty of fluid will help you with 1-2 antidiarrheal tablets ( OTC).
Banana also harden the stool .