I Just Had Rough Penetrative Sex With My Girlfriend (we

I just had rough penetrative sex with my girlfriend (we used a toy). It went on from about 30mins when she realised upon my orgasm that I started bleeding heavily. I stood up and blood was dripping onto my thighs and the floor. We were well lubricated and despite it being rougher than usual, I suppose it should not cause such heavy bleeding. The bleeding has subsided but what is the cause of it? Should I be concerned?