Black holes do not carry baryon number [1] so as long as they were formed before nucleosynthesis that's not a problem. [1] https://en.wikipedia.org/wiki/No-hai

Black holes do not carry baryon number [1] so as long as they were formed before nucleosynthesis that's not a problem. [1] https://en.wikipedia.org/wiki/No-hair_theorem https://en.wikipedia.org/wiki/No-hair_theorem