Most vibrators are used on the outside, against (or near) the clitoris, rather than inside the vagina.
It is possible to get some bleeding after the first time you have something 'penis-sized' inside you - it depends on how your hymen was before and afterwards. Or, depending on how you are inserting it, it could be that you are knocking your cervix.
How big is the larger one? Are you using a lubricant when you insert it?
Is going to a doctor or a sexual health clinic an option? You can always say it is your boyfriend's penis which is that size...