Should I wait for him to make the first move or should I ask him out?

I recently went to prom with my crush and had a great time, and I'm pretty sure he did as well. We're both very shy, and my friend who was helping him ask me had to repeatedly assure him that I wouldn't say no. At the dance, we didn't talk all that much (we were both pretty nervous), but it wasn't as awkward as I expected it to be (except for slow dances). When we were dancing in a circle with our friends, he seemed to bump into me a lot, but I couldn't tell if it was on purpose or just because of the large amount of people. After the dance when he dropped me off, I thanked him for going with me and said that I had a lot of fun. He replied saying that he had a lot of fun as well. We haven't talked much since prom, but I really don't want it to be a one-time thing. However, I doubt that he'll ask me out on his own because he needed a lot of nudging to ask me to prom in the first place. We're also graduating in a week, so maybe he is hesitant to start something so soon before college. Should I wait for him to make the first move or should I ask him out? I don't have his phone number, only facebook messenger, and he is always with friends at school, so I don't know how to go about it.

So sorry for the long rant, and thanks in advance for your replies!

Why not give him your phone number and say "text me when you want to hangout sometime." Hopefully he will get the hint to ask you out. If he texts you, be flirty so it will give him some confidence. If it doesn't work, come back here and we will figure out something else.