The same happened to me once:
"痛o個陣個肚會硬晒唔係咁舒服咁架" But shu shu 之後tissue 會有d pink.
So I asked the Dr. and it is same as what "Haiyu" said. Since I was not regular, it is okay. But from the books, you should check with the Dr. if it is regular.
My Dr. said if there is any blood next time, I must go to hospital....touch wood!