sounds like your uterus was pretty closed and they had to work against it to get it open. They may have bruised your insides a bit!
I would suggest that if you have to go through it again - which hopefully you wont- that you have a/puncture beforehand and afterwards. A/puncture can stimulate the uterus and open it up naturally so that there is no resistenace.
Hang in there and i hope the pain was for a good cause.
Take care

odette