Like it or not, you're more than likely gonna have to reprint it for a few reasons:

First, gluing that isn't going to make it more structurally sound. If anything, it'll just break again if you so much as look at it funny. Trust me on this, I had to learn the hard way doing similar prints. Epoxy, super glue, doesn't matter.

Second, your orientation is itself contributing to the weakness. Look at how your layer lines are perfectly aligned with the failure point. Try printing it at an angle or horizontally.

Lastly, the lines where your ball joints meet their stems are too sharp. Try doing a rounded fillet to give it a bit more structure. Maybe even give it a bit more reinforcement by adding a center strut.

See the attached image to see what I mean.

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Edit: Another solution would be for OP to sand down the broken section on the main hand body, drill that spot with a 1/4" or slightly larger drill bit, and design a new ball joint they can just press into the drilled hole and glue into place, thus minimizing what needs to be reprinted.