Blowjob ?

So I was in a relationship with this guy(my ex) for like 9month we broke up about 3month ago. He hated blowjobs because of previous experience so I wasn't able to do that. But I started dating this amazing guy recently(together since 1month) and once he mentioned that he likes to be given a bj, I would love to give that to him but afraid I might end up hurting him.