Hello,
You had fisting done by your partner. Presently it hurts in your vagina. You are uncomfortable and worried about some serious damage. Fisting requires a lot of lubrication and proper hygiene. The passive partners needs to relax as much as possible otherwise it may cause 
injury, infection or pain that may continue for days. Fisting is one of the extreme forms of sexual activity and less common than anal or 
oral sex.
Fist intercourse is associated with physical 
stress for the passive partner. This sexual practice is popular in BDSM.
If you are a straight heterosexual couple then it is suggested to avoid doing it. If 'conventional' sex occurs after fisting, there is a risk that pathogens will penetrate through injuries to the 
mucous membrane.  This extreme sexual practice carries the risk of injury like 
anal fissure, a painful crack in the skin of the 
anal canal.
Sometimes, irreversible damage may occur as your partner may rupture muscles inside your organ. Fisting can be very painful. Frequent fisting can cause  strong stretching resulting in consequential damage, such as a tendency to 
fecal incontinence. Since you are experiencing pain and discomfort, get clinically examined by a gynecologist, get treated at the earliest.
Take care. Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. Nupur K., General & Family Physician