Boyfriend wants to finger

So my boyfriend and I have an understanding that I’m not having sex until I’m ready and he’s fine with that.... we are in a long distance relationship and dont see each other often and have just started masturbating over ft to each other. We are going to see each other for a day next week and he wants to finger me but I’m going to have my period and he’s fine with that but I feel like it’s going to get messy, how do I go about this?