Have discomfort/ pain after having anul sex could it be brusing and if so how long should I wait til I get it checked out?

It depends. Anal sex or for that matter inserting anything into your anus can cause rectal pain and discomfort. Bruising or even a rectal tear are definite possibilities. It is normal to have some amount of discomfort after anal sex but if it gets worse or doesn't go way see your doctor.