Of course, there are many STIs out there just looking for some moist mucous membranes to inhabit. Now - as many will point out, there are other things one can worry about other than HIV. Also as the insertive partner (the 'top'), your own risk of acquiring HIV is less than 1%, with or without PrEP ().
PrEP reduces risk of acquiring HIV by at least 99% (). A great way to mitigate this risk would be for you both to get tested together, and if you are HIV negative, to consider if PrEP right for you. Condomless anal sex could put you at risk of acquiring HIV if your partner was HIV positive and detectable. Let's say, for instance, that you are asking about HIV risk. The answer to that would rely solely on what your concerns are, and how you've already mitigated these concerns. It sounds like your partner is asking you to share this pleasurable contact with him. Experiencing cum exchanges between two people can be an emotionally powerful and spiritually meaningful experience.
