If you have unprotected anal sex it is a risk.
the anal cavity is a part of the inside of your body. Doesn't matter if there were no lascerations. If you have been exposed to HIV then you need to get tested. You can do so at six weeks and then again at 3 months for a full conclusive result. If you are within a 72 hour window period time from being exposed look into PEP It has the possibility of stopping the HIV virus.